Bug 1363655 - part 7 - make stylo bindgen bits depend on a compile environment; r=rillian

People building without a compilation environment (artifact builds, l10n
builds) won't have a compiler available, let alone the bits to build
bindgen.  We should limit our checks for bindgen-y things accordingly.

toolkit/moz.configure

@@ -623,8 +623,8 @@ id_and_secret_keyfile('Leanplum SDK')
 option('--enable-stylo', nargs='?', choices=('build',),
        help='Include Stylo in the build and/or enable it at runtime')
 
-@depends('--enable-stylo')
-def stylo_config(value):
+@depends('--enable-stylo', '--help')
+def stylo_config(value, _):
     build_stylo = None
     enable_stylo = None
 
@@ -645,8 +645,10 @@ def stylo_config(value):
 option('--disable-stylo-build-bindgen',
        help='Disable build-time bindgen for Stylo')
 
-@depends(stylo_config, '--enable-stylo-build-bindgen')
-def building_stylo_bindgen(stylo_config, bindgen_enabled):
+@depends(stylo_config, '--enable-stylo-build-bindgen', '--enable-compile-environment')
+def building_stylo_bindgen(stylo_config, bindgen_enabled, compile_environment):
+    if not compile_environment:
+        return False
     if not bindgen_enabled:
         return False
     return stylo_config.build
@@ -664,6 +666,7 @@ llvm_config = check_prog('LLVM_CONFIG', ('llvm-config-4.0',
                          when=building_stylo_bindgen,
                          what='llvm-config', allow_missing=True)
 
+with only_when(building_stylo_bindgen):
     option('--with-libclang-path', nargs=1,
            help='Absolute path to a directory containing Clang/LLVM libraries for Stylo (version 3.9.x or above)')
     option('--with-clang-path', nargs=1,
@@ -691,7 +694,7 @@ def check_minimum_llvm_config_version(llvm_config):
             '''.format(version, min_version)))
 
     @depends(llvm_config, '--with-libclang-path', '--with-clang-path',
-         host, when=building_stylo_bindgen)
+             host)
     @imports('os.path')
     @imports(_from='textwrap', _import='dedent')
     def bindgen_config_paths(llvm_config, libclang_path, clang_path,
@@ -719,7 +722,7 @@ def bindgen_config_paths(llvm_config, libclang_path, clang_path,
             # but not have other packages installed.  Since the user is trying
             # to use their system packages, we can't be more specific about what
             # they need.
-        if not os.path.exists(libclang_path)
+            if not os.path.exists(libclang_path):
                 die(dedent('''\
                 The directory {} returned by `llvm-config {}` does not exist.
                 Please check your system configuration.
@@ -759,15 +762,15 @@ def bindgen_config_paths(llvm_config, libclang_path, clang_path,
             clang_path=clang_path[0],
         )
 
+    set_config('MOZ_LIBCLANG_PATH', bindgen_config_paths.libclang_path)
+    set_config('MOZ_CLANG_PATH', bindgen_config_paths.clang_path)
+    set_config('MOZ_STYLO_BINDGEN', depends_if('--enable-stylo-build-bindgen')(lambda _: True))
+
 set_config('MOZ_STYLO', stylo_config.build)
 set_define('MOZ_STYLO', stylo_config.build)
 set_config('MOZ_STYLO_ENABLE', stylo_config.enable)
 set_define('MOZ_STYLO_ENABLE', stylo_config.enable)
 
-set_config('MOZ_LIBCLANG_PATH', bindgen_config_paths.libclang_path)
-set_config('MOZ_CLANG_PATH', bindgen_config_paths.clang_path)
-set_config('MOZ_STYLO_BINDGEN', depends_if('--enable-stylo-build-bindgen')(lambda _: True))
-
 option('--with-servo', env='SERVO_TARGET_DIR', nargs=1,
        help='Absolute path of the target directory where libgeckoservo can '
             'be found. This is generally servo_src_dir/target/release.')