Bug 1483760 Additionally, pass environment variables to cargo if we are not compiling on Windows r=ted

Previously we weren't passing the variables if we were compiling for Windows
when really we only want to do it if we're compiling with MSVC/clang-cl.

The MinGW-Clang build needs this.

Differential Revision: https://phabricator.services.mozilla.com/D3470

--HG--
extra : moz-landing-system : lando

config/rules.mk

@@ -905,7 +905,7 @@ ifdef MOZ_USING_SCCACHE
 sccache_wrap := RUSTC_WRAPPER='$(CCACHE)'
 endif
 
-ifneq (WINNT,$(OS_ARCH))
+ifneq (WINNT,$(HOST_OS_ARCH))
 ifndef MOZ_ASAN
 ifndef MOZ_TSAN
 ifndef MOZ_CODE_COVERAGE