[Test] Remap test should be guarded by caching feature

Update cache path remap test to be correctly guarded by remapping
because if toolchain doesn't support caching, the remap will be
automatically disabled and remap will not happen.

Author: cachemeifyoucan

Tests/SwiftDriverTests/CachingBuildTests.swift

@@ -759,6 +759,9 @@ final class CachingBuildTests: XCTestCase {
                                      "-scanner-prefix-map", path.description + "=/^tmp",
                                      main.nativePathString(escaped: true)] + sdkArgumentsForTesting,
                               env: ProcessEnv.vars)
+      guard driver.isFeatureSupported(.cache_compile_job) else {
+        throw XCTSkip("toolchain does not support caching.")
+      }
       guard driver.isFrontendArgSupported(.scannerPrefixMap) else {
         throw XCTSkip("frontend doesn't support prefix map")
       }