build: re-enable V8 snapshots

Snapshots had been previously disabled because of a security
vunerability. This has been fixed (ref:
https://github.com/iojs/io.js/issues/1631#issuecomment-100101375)

Also, re-enable snapshots for ARMv6 builds. There were previous build
issues that have been fixed.

Fixes: https://github.com/iojs/io.js/issues/1631
PR-URL: https://github.com/iojs/io.js/pull/1663
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

configure

@@ -294,15 +294,15 @@ parser.add_option('--without-perfctr',
     dest='without_perfctr',
     help='build without performance counters')
 
+# Dummy option for backwards compatibility
 parser.add_option('--with-snapshot',
     action='store_true',
-    dest='with_snapshot',
+    dest='unused_with_snapshot',
     help=optparse.SUPPRESS_HELP)
 
-# Dummy option for backwards compatibility.
 parser.add_option('--without-snapshot',
     action='store_true',
-    dest='unused_without_snapshot',
+    dest='without_snapshot',
     help=optparse.SUPPRESS_HELP)
 
 parser.add_option('--without-ssl',
@@ -579,10 +579,6 @@ def configure_arm(o):
     o['variables']['arm_fpu'] = 'vfpv3'
     o['variables']['arm_version'] = '7'
 
-  # Print warning when snapshot is enabled and building on armv6
-  if is_arch_armv6() and options.with_snapshot:
-    warn('when building on ARMv6, don\'t use --with-snapshot')
-
 
 def configure_mips(o):
   can_use_fpu_instructions = (options.mips_float_abi != 'soft')
@@ -604,10 +600,10 @@ def configure_node(o):
   o['variables']['host_arch'] = host_arch
   o['variables']['target_arch'] = target_arch
 
-  if target_arch != host_arch and options.with_snapshot:
-    o['variables']['want_separate_host_toolset'] = 1
-  else:
-    o['variables']['want_separate_host_toolset'] = 0
+  cross_compiling = target_arch != host_arch
+  want_snapshots = not options.without_snapshot
+  o['variables']['want_separate_host_toolset'] = int(
+      cross_compiling and want_snapshots)
 
   if target_arch == 'arm':
     configure_arm(o)
@@ -713,7 +709,7 @@ def configure_v8(o):
   o['variables']['v8_no_strict_aliasing'] = 1  # Work around compiler bugs.
   o['variables']['v8_optimized_debug'] = 0  # Compile with -O0 in debug builds.
   o['variables']['v8_random_seed'] = 0  # Use a random seed for hash tables.
-  o['variables']['v8_use_snapshot'] = b(options.with_snapshot)
+  o['variables']['v8_use_snapshot'] = 0 if options.without_snapshot else 1
 
 def configure_openssl(o):
   o['variables']['node_use_openssl'] = b(not options.without_ssl)

vcbuild.bat

@@ -21,7 +21,7 @@ set snapshot_arg=
 set noprojgen=
 set nobuild=
 set nosign=
-set snapshot=
+set nosnapshot=
 set test_args=
 set msi=
 set licensertf=
@@ -47,7 +47,7 @@ if /i "%1"=="x64"           set target_arch=x64&goto arg-ok
 if /i "%1"=="noprojgen"     set noprojgen=1&goto arg-ok
 if /i "%1"=="nobuild"       set nobuild=1&goto arg-ok
 if /i "%1"=="nosign"        set nosign=1&goto arg-ok
-if /i "%1"=="snapshot"      set snapshot=1&goto arg-ok
+if /i "%1"=="nosnapshot"    set nosnapshot=1&goto arg-ok
 if /i "%1"=="noetw"         set noetw=1&goto arg-ok
 if /i "%1"=="noperfctr"     set noperfctr=1&goto arg-ok
 if /i "%1"=="licensertf"    set licensertf=1&goto arg-ok
@@ -76,7 +76,7 @@ goto next-arg
 :args-done
 if "%config%"=="Debug" set debug_arg=--debug
 if "%target_arch%"=="x64" set msiplatform=x64
-if defined snapshot set snapshot_arg=--with-snapshot
+if defined nosnapshot set snapshot_arg=--without-snapshot
 if defined noetw set noetw_arg=--without-etw& set noetw_msi_arg=/p:NoETW=1
 if defined noperfctr set noperfctr_arg=--without-perfctr& set noperfctr_msi_arg=/p:NoPerfCtr=1