[libc++] Add clang-tidy for the tests

Reviewed By: Mordante, huixie90, #libc

Spies: aheejin, libcxx-commits

Differential Revision: https://reviews.llvm.org/D129976

libcxx/test/.clang-tidy

@@ -0,0 +1,5 @@
+InheritParentConfig: true
+
+CheckOptions:
+  - key:   readability-identifier-naming.ParameterPrefix
+    value: ""

libcxx/test/libcxx/clang_tidy.sh.cpp

@@ -9,7 +9,7 @@
 // REQUIRES: has-clang-tidy
 
 // TODO: run clang-tidy with modules enabled once they are supported
-// RUN: clang-tidy %s --warnings-as-errors=* -header-filter=.* -- -Wweak-vtables -Wno-unknown-warning-option %{compile_flags} -fno-modules
+// RUN: clang-tidy %s --warnings-as-errors=* -header-filter=.* --config-file=%S/../../.clang-tidy -- -Wweak-vtables -Wno-unknown-warning-option %{compile_flags} -fno-modules
 // -Wno-unknown-warning-option tells clang-tidy to ignore '-W' command-line arguments that it doesn't know.
 // There are some GCC-specific ones where clang-tidy would warn otherwise.