[compiler-rt][test] Added REQUIRES:shell to fuzzer test with for-loop (#105557)

This patch makes the features_dir.test file require a shell when
running. This will make the test file unsupported when running llvm-lit
with its internal shell implementation, which is enabled by turning on
the LIT_USE_INTERNAL_SHELL environment variable. Lit's internal shell
currently does not support for-loop syntax.

Author: connieyzhu

compiler-rt/test/fuzzer/features_dir.test

@@ -1,5 +1,5 @@
 # Tests -features_dir=F
-# REQUIRES: linux
+# REQUIRES: linux, shell
 RUN: %cpp_compiler %S/SimpleTest.cpp -o %t-SimpleTest
 RUN: rm -rf %t-C %t-F
 RUN: mkdir %t-C %t-F