build: adding LTO support to configure script

There is now a --chakracore-lto-build flag which will attempt to
build node-chakracore using link time optimisations. This is not
guaranteed to work without providing the correct build environment,
which includes using compatible versions of `ar`, `ranlib`, and `ld`.

PR-URL: #341
Reviewed-By: Kyle Farnung <[email protected]>

configure

@@ -487,6 +487,13 @@ parser.add_option('--chakracore-ninja-build',
     default=False,
     help='Enable build of ChakraCore using ninja (requires engine to be ChakraCore)')
 
+parser.add_option('--chakracore-lto-build',
+    action='store_true',
+    dest='chakracore_lto_build',
+    default=False,
+    help='Enable build of ChakraCore using LTO (requires engine to be ChakraCore)')
+
+
 parser.add_option('--shared',
     action='store_true',
     dest='shared',
@@ -1340,6 +1347,13 @@ def configure_engine(o):
       o['variables']['chakracore_parallel_build_flags'] = [ "--ninja" ]
     else:
       o['variables']['chakracore_parallel_build_flags'] = []
+    if options.chakracore_lto_build:
+      o['variables']['chakracore_use_lto'] = "true"
+      o['variables']['chakracore_lto_build_flags'] = [ "--lto" ]
+    else:
+      o['variables']['chakracore_use_lto'] = "false"
+      o['variables']['chakracore_lto_build_flags'] = [ ]
+
 
 
 output = {

deps/chakrashim/chakracore.gyp

@@ -122,6 +122,7 @@
                 '--without=Simdjs',
                 '--static',
                 '<@(chakracore_parallel_build_flags)',
+                '<@(chakracore_lto_build_flags)',
                 '<@(chakra_build_flags)',
                 '<@(icu_args)',
                 '--libs-only'

node.gyp

@@ -271,6 +271,13 @@
           'sources': [
             'src/node_api_jsrt.cc',
           ],
+          'conditions': [
+            [ 'OS!="win" and chakracore_use_lto=="true"', {
+              'ldflags': [
+                '-flto',
+              ],
+            }],
+          ],
         }, {
           'sources': [
             'src/node_api.cc',
@@ -698,7 +705,14 @@
           ],
           'sources!': [
             'test/cctest/test_environment.cc', # TODO: Enable these test for node-chakracore
-          ]
+          ],
+          'conditions': [
+            [ 'OS!="win" and chakracore_use_lto=="true"', {
+              'ldflags': [
+                '-flto',
+              ],
+            }],
+          ],
         }],
         ['v8_enable_inspector==1', {
           'sources': [