bug 1409276 - disable warnings-as-errors for Rust libraries/programs. r=chmanchester

When compiling C/C++ sources via Rust build scripts there's no point in
enabling warnings-as-errors as all such code is third-party code.

MozReview-Commit-ID: 5pGH6w9ZE2I

--HG--
extra : rebase_source : ad36be6aed39d55055728f85b799adf5f0cf0f4b

build/templates.mozbuild

@@ -53,6 +53,9 @@ def Library(name):
     '''Template for libraries.'''
     LIBRARY_NAME = name
 
+@template
+def AllowCompilerWarnings():
+    COMPILE_FLAGS['WARNINGS_AS_ERRORS'] = []
 
 @template
 def RustLibrary(name, features=None, target_dir=None):
@@ -60,6 +63,8 @@ def RustLibrary(name, features=None, target_dir=None):
     Library(name)
 
     IS_RUST_LIBRARY = True
+    # Some Rust build scripts compile C/C++ sources, don't error on warnings for them.
+    AllowCompilerWarnings()
 
     if features:
         RUST_LIBRARY_FEATURES = features
@@ -125,6 +130,8 @@ def HostRustLibrary(name, features=None):
     HostLibrary(name)
 
     IS_RUST_LIBRARY = True
+    # Some Rust build scripts compile C/C++ sources, don't error on warnings for them.
+    AllowCompilerWarnings()
 
     if features:
         HOST_RUST_LIBRARY_FEATURES = features
@@ -137,10 +144,6 @@ def DisableStlWrapping():
 def NoVisibilityFlags():
     COMPILE_FLAGS['VISIBILITY'] = []
 
-@template
-def AllowCompilerWarnings():
-    COMPILE_FLAGS['WARNINGS_AS_ERRORS'] = []
-
 @template
 def ForceInclude(*headers):
     """Force includes a set of header files in C++ compilations"""

testing/geckodriver/moz.build

@@ -3,6 +3,8 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 RUST_PROGRAMS += ["geckodriver"]
+# Some Rust build scripts compile C/C++ sources, don't error on warnings for them.
+AllowCompilerWarnings()
 
 # https://bugzil.la/1425365
 if CONFIG["OS_ARCH"] != "WINNT":