Add experimental support for compiling with clang and ASan on Linux.

build/standalone.gypi

Index: build/standalone.gypi
diff --git a/build/standalone.gypi b/build/standalone.gypi
index c0eaef419df30e2ff6538aed44e0940d87aa128d..fa171314ef573395920117746491ee117bad4856 100644
--- a/build/standalone.gypi
+++ b/build/standalone.gypi
@@ -8,6 +8,8 @@
   'variables': {
     'component%': 'static_library',
     'clang%': 0,
+    'asan%': 0,
+    'sanitizer_coverage%': 0,
     'msvs_multi_core_compile%': '1',
     'variables': {
       'variables': {
@@ -37,6 +39,7 @@
       'host_arch%': '<(host_arch)',
       'target_arch%': '<(target_arch)',
     },
+    'clang_dir%': 'third_party/llvm-build/Release+Asserts',
     # These two are needed by V8.
     'host_arch%': '<(host_arch)',
     'target_arch%': '<(target_arch)',
@@ -50,6 +53,11 @@
       }, {
         'os_posix%': 1,
       }],
+      ['OS=="linux" or OS=="mac"', {
+        'clang%': 1,
+      }, {
+        'clang%': 0,
+      }],
     ],
   },
   'target_defaults': {
@@ -161,6 +169,22 @@
     'ldflags': [
       '-pthread',
     ],
+    'conditions': [
+      ['asan==1', {
+        'cflags': [
+          '-fsanitize=address',
+          '-gline-tables-only',
+        ],
+        'ldflags': [
+          '-fsanitize=address',
+        ],
+      }],
+      ['sanitizer_coverage!=0', {
+        'cflags': [
+          '-fsanitize-coverage=<(sanitizer_coverage)',
+        ],
+      }],
+    ],
     'defines': [
       # Don't use deprecated V8 APIs anywhere.
       'V8_DEPRECATION_WARNINGS',
@@ -250,6 +274,16 @@
         '-fPIC',
       ],
     }],
+    ['OS=="linux" or OS=="mac"', {
+      'conditions': [
+        ['clang==1', {
+          'make_global_settings': [
+            ['CC', '<(clang_dir)/bin/clang'],
+            ['CXX', '<(clang_dir)/bin/clang++'],
+          ],
+        }],
+      ],
+    }],  # OS=="linux" or OS=="mac"
     ['OS=="win"', {
       'target_defaults': {
         'defines': [