fix(@angular/build): direct check include file exists in unit-test discovery

When discovering unit-test files, the `include` option values that are
not dynamic patterns will now be checked directly if they exist on the
file system. This avoids glob calls for specific files and helps avoid
Windows pathing issues with glob syntax.

Author: clydin

packages/angular/build/src/builders/unit-test/test-discovery.ts

@@ -232,15 +232,15 @@ async function resolveStaticPattern(
     return { resolved: [], unresolved: [`${pattern}/**/*.@(${infixes}).@(ts|tsx)`] };
   }
 
-  const fileExt = extname(pattern);
-  const baseName = basename(pattern, fileExt);
+  if (await exists(fullPath)) {
+    return { resolved: [fullPath], unresolved: [] };
+  }
+
+  const fileExt = extname(fullPath);
+  const baseName = basename(fullPath, fileExt);
 
   for (const infix of TEST_FILE_INFIXES) {
-    const potentialSpec = join(
-      projectSourceRoot,
-      dirname(pattern),
-      `${baseName}${infix}${fileExt}`,
-    );
+    const potentialSpec = join(dirname(fullPath), `${baseName}${infix}${fileExt}`);
     if (await exists(potentialSpec)) {
       return { resolved: [potentialSpec], unresolved: [] };
     }