Bug 1473436 - Disable elfhack on local builds. r=chmanchester

Because of bug 1423822, we can't enable elfhack and lld at the same
time. OTOH, elfhack is not really useful on local builds: it's only used
on `make package`. Since we're going to make lld the default if it's
available, let's just completely disable elfhack by default on local
builds.

While here, hide the configure flag when compile environment is
disabled.

--HG--
extra : rebase_source : 154d3059db4f0f073bd219670ef4c9bc6ebcfd26

toolkit/moz.configure

@@ -1178,16 +1178,22 @@ add_old_configure_assignment('MOZ_ASAN_REPORTER', enable_asan_reporter)
 
 # Elfhack
 # ==============================================================
-@depends(host, target)
-def has_elfhack(host, target):
-    return target.kernel == 'Linux' and host.kernel == 'Linux' and \
-           target.cpu in ('arm', 'x86', 'x86_64')
+with only_when('--enable-compile-environment'):
+    @depends(host, target)
+    def has_elfhack(host, target):
+        return target.kernel == 'Linux' and host.kernel == 'Linux' and \
+               target.cpu in ('arm', 'x86', 'x86_64')
 
-with only_when(has_elfhack):
-    option('--disable-elf-hack', help='Disable elf hacks')
+    @depends('--enable-release')
+    def default_elfhack(release):
+        return bool(release)
 
-    set_config('USE_ELF_HACK',
-               depends_if('--enable-elf-hack')(lambda _: True))
+    with only_when(has_elfhack):
+        option('--disable-elf-hack', default=default_elfhack,
+               help='Disable elf hacks')
+
+        set_config('USE_ELF_HACK',
+                   depends_if('--enable-elf-hack')(lambda _: True))
 
 
 @depends(check_build_environment)