Allow customization of GYP_DEFINES

[teradiot]

No description provided.

[ignisf]

Hello,

Sorry for taking so much time to get to your PR. What is the behaviour you're looking for? Having the GYP_DEFINES environment variable be taken into account when building libv8?

[teradiot]

Sorry for not explaining enough.

I encountered the following error when I built libv8 from source on Alpine Linux.

Building v8 with env CXX=g\+\+ LINK=g\+\+ /usr/bin/make x64.release i18nsupport=off werror=no GYP_DEFINES="v8_use_external_startup_data=0 linux_use_bundled_gold=0 clang=0"
PYTHONPATH="/usr/local/bundle/gems/libv8-5.3.332.38.3/vendor/v8/tools/generate_shim_headers:/usr/local/bundle/gems/libv8-5.3.332.38.3/vendor/v8/gypfiles::/usr/local/bundle/gems/libv8-5.3.332.38.3/vendor/v8/tools/gyp/pylib:" \
GYP_GENERATORS=make \
tools/gyp/gyp --generator-output="out" gypfiles/all.gyp \
              -Igypfiles/standalone.gypi --depth=. \
              -Dv8_target_arch=x64 \
               -Dtarget_arch=x64 \
               \
              -S.x64.release  -Dv8_enable_backtrace=1 -Dwerror='' -Dv8_enable_i18n_support=0 -Darm_fpu=default -Darm_float_abi=default
make[1]: Entering directory '/usr/local/bundle/gems/libv8-5.3.332.38.3/vendor/v8/out'
  CXX(target) /usr/local/bundle/gems/libv8-5.3.332.38.3/vendor/v8/out/x64.release/obj.target/v8_base/src/accessors.o
g++: error trying to exec '/usr/local/bundle/gems/libv8-5.3.332.38.3/vendor/v8/third_party/binutils/Linux_x64/Release/bin/as': execv: No such file or directory
src/v8_base.target.x64.release.mk:555: recipe for target '/usr/local/bundle/gems/libv8-5.3.332.38.3/vendor/v8/out/x64.release/obj.target/v8_base/src/accessors.o' failed
make[1]: *** [/usr/local/bundle/gems/libv8-5.3.332.38.3/vendor/v8/out/x64.release/obj.target/v8_base/src/accessors.o] Error 1
make[1]: Leaving directory '/usr/local/bundle/gems/libv8-5.3.332.38.3/vendor/v8/out'
Makefile:314: recipe for target 'x64.release' failed
make: *** [x64.release] Error 2
/usr/local/bundle/gems/libv8-5.3.332.38.3/ext/libv8/location.rb:41:in `block in verify_installation!': libv8 did not install properly, expected binary v8 archive '/usr/local/bundle/gems/libv8-5.3.332.38.3/vendor/v8/out/x64.release/obj.target/tools/gyp/libv8_base.a'to exist, but it was not found (Libv8::Location::Vendor::ArchiveNotFound)
        from /usr/local/bundle/gems/libv8-5.3.332.38.3/ext/libv8/location.rb:40:in `each'
        from /usr/local/bundle/gems/libv8-5.3.332.38.3/ext/libv8/location.rb:40:in `verify_installation!'
        from /usr/local/bundle/gems/libv8-5.3.332.38.3/ext/libv8/location.rb:26:in `install!'
        from extconf.rb:7:in `<main>'
ERROR:  Error installing libv8-5.3.332.38.3.gem:
        ERROR: Failed to build gem native extension.

Details are here.
Https://gist.github.com/teradiot/d76ded67ad915b11d9ff125100cc0cee/a6aa33e0c25d66e7bf659998276ed0a9f72ff3b6

I solved this problem by setting GYP_DEFINES.

export GYP_DEFINES="linux_use_bundled_binutils=0 linux_use_bundled_gold=0"

https://gist.github.com/teradiot/d76ded67ad915b11d9ff125100cc0cee/revisions

So I need to be able to set GYP_DEFINES when building libv8.