Bug 1557785 - Allow LLVM_PROFDATA to work even if not explicitly set in the environment; r=firefox-build-system-reviewers,chmanchester

Windows finds llvm-profdata in the PATH, in contrast to Linux or Android
builds that set LLVM_PROFDATA as an environment variable in mozconfigs.
The pgo_profile_path() configure checks should still work in this case.

Differential Revision: https://phabricator.services.mozilla.com/D34799

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

build/moz.configure/toolchain.configure

@@ -1485,7 +1485,7 @@ set_config('MOZ_PROFILE_USE',
            depends_if('--enable-profile-use')(lambda _: True))
 
 
-@depends('--with-pgo-profile-path', '--enable-profile-use', 'LLVM_PROFDATA')
+@depends('--with-pgo-profile-path', '--enable-profile-use', llvm_profdata)
 @imports('os')
 def pgo_profile_path(path, pgo_use, profdata):
     if not path: