MIPS64: Enable shorten-64-to-32 warning.

build/standalone.gypi

Index: build/standalone.gypi
diff --git a/build/standalone.gypi b/build/standalone.gypi
index 6d3d55d4c4cc89457c00f494ba8c93e339df3177..b0b503f9af99c220362d3c094c0b138c9f91a4e4 100644
--- a/build/standalone.gypi
+++ b/build/standalone.gypi
@@ -473,7 +473,8 @@
         ],
         'ldflags': [ '-pthread', ],
         'conditions': [
-          [ 'clang==1 and (v8_target_arch=="x64" or v8_target_arch=="arm64")', {
+          [ 'clang==1 and (v8_target_arch=="x64" or v8_target_arch=="arm64" \
+            or v8_target_arch=="mips64el")', {
             'cflags': [ '-Wshorten-64-to-32' ],
           }],
           [ 'host_arch=="ppc64" and OS!="aix"', {
@@ -657,6 +658,12 @@
               'GCC_VERSION': 'com.apple.compilers.llvm.clang.1_0',
               'CLANG_CXX_LANGUAGE_STANDARD': 'gnu++0x',  # -std=gnu++0x
             },
+            'conditions': [
+              ['v8_target_arch=="x64" or v8_target_arch=="arm64" \
+                or v8_target_arch=="mips64el"', {
+                'xcode_settings': {'WARNING_CFLAGS': ['-Wshorten-64-to-32']},
+              }],
+            ]
           }],
         ],
         'target_conditions': [