Remove glibc dependency, statically link binaries to musl

[hannobraun]

I'm currently having a problem with the production server:

/opt/vndf/vndf-game-service: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.17' not found (required by /opt/vndf/vndf-game-service)

The problem here is, that some symbols in libc are used, that are only available in glibc 2.17.

Research shows, that the clock-related functions are to blame:

$ objdump -p output/bin/vndf-game-service
...
required from libc.so.6:
0x06969194 0x00 16 GLIBC_2.14
0x0d696913 0x00 14 GLIBC_2.3
0x0d696914 0x00 11 GLIBC_2.4
0x09691974 0x00 09 GLIBC_2.3.4
0x06969197 0x00 08 GLIBC_2.17
0x0d696917 0x00 07 GLIBC_2.7
0x09691972 0x00 05 GLIBC_2.3.2
0x09691a75 0x00 03 GLIBC_2.2.5

$ objdump -T output/bin/vndf-game-service | grep GLIBC_2.17
0000000000000000 DF UND 0000000000000000 GLIBC_2.17 clock_gettime
0000000000000000 DF UND 0000000000000000 GLIBC_2.17 clock_getres

Unfortunately, older versions of the symbols don't seem to be available:

$ objdump -T /lib/x86_64-linux-gnu/libc.so.6 | grep -w clock_gettime
000000000010f950 g DF .text 000000000000003b GLIBC_2.17 clock_gettime
$ objdump -T /lib/x86_64-linux-gnu/libc.so.6 | grep -w clock_getres
000000000010f8f0 g DF .text 0000000000000053 GLIBC_2.17 clock_getres

I'm attempting to solve this problem by just not referencing any clock-related functions for now. Of course, this isn't a good solution.

I see two good ways to solve this:

• Practical: Build any binaries on their target platform. This requires better build infrastructure.
• Ideal: Statically link libc, for example using musl (http://www.musl-libc.org/). I like this a lot, since it would solve any libc versioning problems once and for all. However, this might not be easy to do.

[hannobraun]

+1, see #61

[hannobraun]

Changed the title of this issue from a problem description to a description of the solution. Removing bug tag, adding enhancement tag.

I think this should best be done by improving Rust directly. There's an existing issue for this that explicitly mentions musl: rust-lang/rust#7283

[hannobraun]

+1, due to #62

[hannobraun]

+1, failed to run the client on my mom's laptop due to glibc

[hannobraun]

Adding the priority tag. This absolutely must be solved before VNDF can see widespread use.