Bug 1467319 - Generate fewer redundant conditions when generating moz.build files fron gn configs. r=mshal

MozReview-Commit-ID: Ef67haFgx3A

--HG--
extra : rebase_source : b71a870aa4d838cd0230ed07819cf3f3ced5d1d4

python/mozbuild/mozbuild/gn_processor.py

@@ -439,7 +439,10 @@ def write_mozbuild(config, srcdir, output, non_unified_sources, gn_config_files,
             # for every configuration, then factor by other potentially useful
             # combinations.
             for attrs in ((),
-                          ('MOZ_DEBUG',), ('OS_TARGET',), ('MOZ_DEBUG', 'OS_TARGET',),
+                          ('MOZ_DEBUG',), ('OS_TARGET',), ('CPU_ARCH',),
+                          ('MOZ_DEBUG', 'OS_TARGET',),
+                          ('OS_TARGET', 'CPU_ARCH'),
+                          ('OS_TARGET', 'CPU_ARCH', 'MOZ_DEBUG'),
                           ('MOZ_DEBUG', 'OS_TARGET', 'CPU_ARCH', 'HOST_CPU_ARCH')):
                 conditions = set()
                 for args in all_args: