ohos: fix ohos.c test case error with LLVM_ENABLE_PER_TARGET_RUNTIME_DIR=OFF

The problem is because libclang_rt.builtins-{arch}.a for all the
arches will be installed into the same folder with old compiler rt
layout (LLVM_ENABLE_PER_TARGET_RUNTIME_DIR=OFF) and OHOS driver will
get a wrong library in this case. To fix the problem, `-ohos`
suffix will be added to the ohos builtin libraries search path.

Note: OHOS driver doesn't support the old layout,
${arch}-linux-unknown-ohos targets have to be built with
LLVM_ENABLE_PER_TARGET_RUNTIME_DIR=ON

Author: phuang

clang/lib/Driver/ToolChain.cpp

@@ -745,7 +745,11 @@ std::string ToolChain::buildCompilerRTBasename(const llvm::opt::ArgList &Args,
   std::string ArchAndEnv;
   if (AddArch) {
     StringRef Arch = getArchNameForCompilerRTLib(*this, Args);
-    const char *Env = TT.isAndroid() ? "-android" : "";
+    const char *Env = "";
+    if (TT.isAndroid())
+      Env = "-android";
+    else if (TT.isOHOSFamily())
+      Env = "-ohos";
     ArchAndEnv = ("-" + Arch + Env).str();
   }
   return (Prefix + Twine("clang_rt.") + Component + ArchAndEnv + Suffix).str();