[Clang] Redisable two tests on Windows

These two tests started failing after being enabled again on Windows due
to the removal of their shell requirements now that they can execute
with lit's internal shell. However, they use forward slashes in file
paths in FileCheck assertions, which has been leading to failures on
certain bots.

https://lab.llvm.org/buildbot/#/builders/46/builds/22798
https://lab.llvm.org/buildbot/#/builders/193/builds/10297

Author: boomanaiden154

clang/test/Driver/env.c

@@ -1,3 +1,5 @@
+// Some assertions in this test use Linux style (/) file paths.
+// UNSUPPORTED: system-windows
 // The PATH variable is heavily used when trying to find a linker.
 // RUN: env -i LC_ALL=C LD_LIBRARY_PATH="$LD_LIBRARY_PATH" CLANG_NO_DEFAULT_CONFIG=1 \
 // RUN:   %clang %s -### -o %t.o --target=i386-unknown-linux \

clang/test/Modules/crash-vfs-path-traversal.m

@@ -1,5 +1,7 @@
 // REQUIRES: crash-recovery
 // UNSUPPORTED: ms-sdk, target={{.*-(ps4|ps5)}}
+// Some assertions in this test use Linux style (/) file paths.
+// UNSUPPORTED: system-windows
 
 // FIXME: Canonicalizing paths to remove relative traversal components
 // currenty fails a unittest on windows and is disable by default.