Removed GPR_POSIX_FILE, and changed the files that used it
diff --git a/gRPC-Core.podspec b/gRPC-Core.podspec
index 753dabe..b7a5e72 100644
--- a/gRPC-Core.podspec
+++ b/gRPC-Core.podspec
@@ -533,8 +533,7 @@
                       'src/core/lib/security/credentials/credentials.c',
                       'src/core/lib/security/credentials/credentials_metadata.c',
                       'src/core/lib/security/credentials/fake/fake_credentials.c',
-                      'src/core/lib/security/credentials/google_default/credentials_posix.c',
-                      'src/core/lib/security/credentials/google_default/credentials_windows.c',
+                      'src/core/lib/security/credentials/google_default/credentials_generic.c',
                       'src/core/lib/security/credentials/google_default/google_default_credentials.c',
                       'src/core/lib/security/credentials/iam/iam_credentials.c',
                       'src/core/lib/security/credentials/jwt/json_token.c',