Link against libboost_regex correctly on travis

.travis.yml

@@ -3,7 +3,5 @@ compiler:
     - gcc
 before_install:
   - sudo apt-get install libboost-regex1.48-dev
-env:
-  - CXXFLAGS='-D USE_BOOST_REGEX' LDFLAGS='-lboost_regex'
-install: script/configure.sh
+install: script/configure.sh -D USE_BOOST_REGEX
 script: script/test.sh

script/configure.sh

@@ -3,5 +3,17 @@
 set -e
 
 git submodule update --init
-externals/gyp/gyp tree_sitter.gyp --depth .
-externals/gyp/gyp tree_sitter.gyp --depth . --format=make
+externals/gyp/gyp tree_sitter.gyp --depth . --format=make $@
+
+if [ $1 == "-h" ]; then
+  cat <<-HELP
+
+Variables:
+
+-D USE_BOOST_REGEX - Use boost regex library for tests, not the built-in regex
+                     library. This is useful when linking against an older
+                     version of the standard library. libboost_regex must be
+                     installed.
+
+HELP
+fi

tree_sitter.gyp

@@ -63,6 +63,15 @@
         'examples',
         'spec/runtime',
       ],
+      'variables': {
+        'USE_BOOST_REGEX%': 'false',
+      },
+      'conditions': [
+        ['USE_BOOST_REGEX != "false"', {
+          'defines': ['USE_BOOST_REGEX'],
+          'libraries': ['-lboost_regex'],
+        }]
+      ],
       'sources': [
         '<!@(find spec/runtime -name "*.h" -or -name "*.cc")',
         '<!@(find examples/parsers -name "*.c")',