[Clang] Search for 'offload-arch' only next to the clang driver (#150965)

Summary:
Previously, querying for the offload architecture tool would invoke the
user's PATH, which is bad when potentially using the driver from a
direct path. This patch change this to *only* consider the
`offload-arch` that's supposed to live next to the driver executable.
Now we will no longer pick up a potentially conflicting version of this
tool and it should always be found (Since it's a clang tool that's
installazed alongside the driver)

Author: jhuber6

clang/lib/Driver/Driver.cpp

@@ -910,7 +910,7 @@ getSystemOffloadArchs(Compilation &C, Action::OffloadKind Kind) {
 
   SmallVector<std::string> GPUArchs;
   if (llvm::ErrorOr<std::string> Executable =
-          llvm::sys::findProgramByName(Program)) {
+          llvm::sys::findProgramByName(Program, {C.getDriver().Dir})) {
     llvm::SmallVector<StringRef> Args{*Executable};
     if (Kind == Action::OFK_HIP)
       Args.push_back("--only=amdgpu");