Improve support for brew install openssl on OSX

[bartonjs]

The test for algorithm_enc vs algorithms was using only the default includes path. Now it
also includes the place where find_package found the openssl headers, so the test executes
successfully, leading to a successful compilation.

brew install openssl
brew link --force openssl
./build.sh clean native

cc: @sokket @eerhardt @stephentoub

[jonmill]

Great work!! Thanks for finding the fix, works on my 10.10 box :) LGTM

[eerhardt]

LGTM

[bartonjs]

I guess I should say "this is on the road to fixing #3924", because on 10.11 the headers only go to /usr/local/include/openssl, which doesn't seem to be part of the search path that check_struct_has_member uses by default.

[ghost]

@bartonjs, @sokket, I forgot to mention here: #4026 (comment) that I had to make another change, i.e. rename #include<algorithms.h> to #include<algorithm2.h> to make it build on El Capitan. Is it something you guys are experiencing too or my installation got whacked somehow (due to unusual 2 suffix)?

[stephentoub]

LGTM

[bartonjs]

@jasonwilliams200OK I didn't have to do anything special other than this PR. My set of instructions were

• A bunch of stuff that lead me to wiping the hard drive, so not relevant
• Clean install 10.11
• Install XCode, hoping that I could pull the files from the 10.10 SDK (no joy)
• Follow https://github.com/dotnet/coreclr/blob/master/Documentation/building/osx-instructions.md up through getting CMake
• brew install openssl
• Do lots of building/debugging-cmakes-decisions
• brew link --force openssl
• Do more building/debugging-cmakes-decisions
• End up with this one line change as all that was required to build both coreclr and corefx (native).

So it... should... be happy? 😄

[ghost]

@bartonjs, this is fantastic! I just cloned and built master (incl. your commits) on El Capitan, with this CMake magic i didn't had to change algorithms to algorithms2 either. So thank you! 😄