Fix build failures with GCC

It seems that the GYP configuration assumes that every x86/x86_64 MacOS
or Linux system is using clang. State explicitly to GYP that we are not
using clang whenever we are not using clang.

See discussion in 6786a2c4c2

.travis.yml

@@ -5,13 +5,27 @@ rvm:
   - 2.0.0
   - 1.9.3
   - rbx-2
-bundler_args: -j4
+matrix:
+  include:
+    - rvm: ruby-2.2.2-clang
+      env: CXX=clang++
+    - rvm: ruby-head
+    - rvm: ruby-head-clang
+      env: CXX=clang++
+    - rvm: ree
+    - rvm: ruby-1.8.7
+  allow_failures:
+    - rvm: ree
+    - rvm: ruby-1.8.7
+    - rvm: ruby-head
+    - rvm: ruby-head-clang
+  fast_finish: true
+bundler_args: -j4 --retry=3
 script:
-  - bundle exec rake spec build binary --trace
-  - travis_wait gem install pkg/*.gem
+  - MAKEFLAGS+=-j8 bundle exec rake spec build binary --trace
+  - MAKEFLAGS+=-j8 travis_wait gem install pkg/*.gem
 notifications:
   recipients:
     - cowboyd@thefrontside.net
     - bordjukov@gmail.com
-cache: bundler
-env: CXX=clang++
+cache: bundler

ext/libv8/builder.rb

@@ -33,9 +33,8 @@ module Libv8
       # default.
       flags << "ARFLAGS.target=crs"
 
-      # Pass clang=1 to GYP as noted in wiki
-      # https://code.google.com/p/v8/wiki/BuildingWithGYP#Clang_+_make
-      flags << 'GYP_DEFINES="clang=1"' if @compiler.is_a? Compiler::Clang
+      # Pass clang flag to GYP in order to work around GCC compilation failures
+      flags << "GYP_DEFINES=\"clang=#{@compiler.is_a?(Compiler::Clang) ? '1' : '0'}\""
 
       # Disable i18n
       flags << 'i18nsupport=off'