Allow multiple Scala Native versions

[lolgab]

This change allows multiple versions of Scala Native.

[non]

@lolgab I've never been able to successfully run native/test. What's the best way for me to figure out how to do this?

(I realize it's not your job to help debug my Scala Native problems, but for me to do a release with Scala Native I need to get this working. I did follow the Scala Native instructions.)

I can build fine:

sbt:scalacheck> native/clean
[success] Total time: 1 s, completed Aug 8, 2019 1:17:17 PM
sbt:scalacheck> native/compile
sbt:scalacheck> native/compile
[info] Updating native...
[info] Done updating.
[info] Compiling 21 Scala sources to /Users/erik/w/scalacheck/native/target/scala-2.11/classes ...
[info] Done compiling.

But when I go to run native/test I see:

sbt:scalacheck> native/test
[info] Compiling 7 Scala sources to /Users/erik/w/scalacheck/native/target/scala-2.11/test-classes ...
[info] Done compiling.
[info] Compiling 1 Scala source to /Users/erik/w/scalacheck/native/target/scala-2.11/test-classes ...
[info] Done compiling.
[info] Linking (3279 ms)
[info] Discovered 2499 classes and 15331 methods
[info] Optimizing (debug mode) (4344 ms)
[info] Generating intermediate code (1589 ms)
[info] Produced 58 files
[info] Compiling to native code (2647 ms)
[error] /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/cpio.c:1:10: fatal error: 'cpio.h' file not found
[error] /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/platform.c:4:10: fatal error: 'sys/utsname.h' file not found
[error] /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/gc/immix/Marker.c:1:10: fatal error: 'stdio.h' file not found
[error] #include <stdio.h>
[error] /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/pwd.c:1:10: fatal error: 'stdlib.h' file not found
[error]          ^
[error] #include <sys/utsname.h>
[error] #include <stdlib.h>
[error]          ^
[error]          ^
[error] In file included from /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/sys/socket_conversions.c:1:
[error] #include <cpio.h>
[error] /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/sys/../netinet/in.h:4:10: fatal error: 'netinet/in.h' file not found
[error] /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/grp.c:1:10: fatal error: 'stdlib.h' file not found
[error] /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/arpa/inet.c:1:10: fatal error: 'arpa/inet.h' file not found
[error] #include <netinet/in.h>
[error]          ^
[error]          ^
[error] #include <arpa/inet.h>
[error] #include <stdlib.h>
[error]          ^
[error]          ^
[error] In file included from /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.c:1:
[error] /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.h:1:10: error: 'netdb.h' file not found with <angled> include; use "quotes" instead
[error] #include <netdb.h>
[error]          ^~~~~~~~~
[error]          "netdb.h"
[error] In file included from /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.c:1:
[error] In file included from /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.h:1:
[error] /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.h:1:10: error: 'netdb.h' file not found with <angled> include; use "quotes" instead
[error] #include <netdb.h>
[error]          ^~~~~~~~~
[error]          "netdb.h"
[error] In file included from /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.c:1:
[error] In file included from /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.h:1:
[error] In file included from /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.h:1:
[error] /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.h:1:10: error: 'netdb.h' file not found with <angled> include; use "quotes" instead
[error] #include <netdb.h>
[error]          ^~~~~~~~~
[error]          "netdb.h"
[error] In file included from /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.c:1:
[error] In file included from /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.h:1:
[error] In file included from /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.h:1:
[error] In file included from /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.h:1:
[error] /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.h:1:10: error: 'netdb.h' file not found with <angled> include; use "quotes" instead
[error] #include <netdb.h>
[error]          ^~~~~~~~~
[error]          "netdb.h"
[error] In file included from /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.c:1:
[error] In file included from /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.h:1:
[error] In file included from /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.h:1:
[error] In file included from /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.h:1:
[error] In file included from /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.h:1:
[error] /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.h:1:10: error: 'netdb.h' file not found with <angled> include; use "quotes" instead
[error] #include <netdb.h>
[error]          ^~~~~~~~~
[error]          "netdb.h"
[error] In file included from /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.c:1:
[error] In file included from /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.h:1:
[error] In file included from /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.h:1:
[error] In file included from /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.h:1:
[error] In file included from /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.h:1:
[error] In file included from /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.h:1:
[error] /Users/erik/w/scalacheck/native/target/scala-2.11/native/lib/posix/netdb.h:1:10: error: 'netdb.h' file not found with <angled> include; use "quotes" instead
[error] #include <netdb.h>
[error]          ^~~~~~~~~
[error]          "netdb.h"

[lolgab]

Did you try to install xcode clang?

xcode-select --install

I am on a Mac Mojave machine and it works.
I'm happy to help you and I understand you don't want to release a software without testing it yourself.

[non]

I do have the command line tools installed:

$ xcode-select --install
xcode-select: error: command line tools are already installed, use "Software Update" to install updates

(EDIT: according to Software Update I am up-to-date.)

[non]

Update: I got the native build working on my other computer. I'm going to confirm that this works locally and then I'll be happy to merge. Thanks for bearing with me.

(I still can't figure out why it doesn't work on the first computer, which is frustrating.)

[lolgab]

Don't forget to publish for 0.3.9 and 0.4.0-M2 using the environment variable if you do :)

[non]

Just confirmed again that this PR works locally (on my machine that is able to run Scala Native).