[clang][Driver] Add ROCm lib/llvm/bin detection test

Add a lit test that exercises RocmInstallationDetector when clang is installed
under /opt/rocm/lib/llvm/bin, using a synthetic sysroot so it does not depend
on any real /opt/rocm installation. The test copies the built clang binary
into the test tree so the driver observes the expected InstalledDir and real
path, following the precedent of other driver tests that copy %clang into a
temporary layout.

Author: yxsamliu

clang/test/Driver/rocm-detect-lib-llvm.hip

@@ -0,0 +1,28 @@
+// UNSUPPORTED: system-windows
+//
+// Copying clang to a new location and running it will not work unless it is
+// statically linked. Dynamically linked builds typically use relative rpaths,
+// which this will break.
+// REQUIRES: static-libs
+//
+// Test detecting ROCm installation from clang installed in /opt/rocm/lib/llvm/bin.
+// This exercises the RocmInstallationDetector logic that backs up from
+// /opt/rocm/lib/llvm/bin to the ROCm root, while avoiding dependence on any
+// real /opt/rocm installation by using a synthetic sysroot under %t.
+//
+// RUN: rm -rf %t/*
+// Set up a fake ROCm installation rooted at /opt/rocm in the synthetic sysroot
+// so that the device libraries and HIP runtime can be found.
+// RUN: mkdir -p %t/sysroot/opt/rocm
+// RUN: cp -r %S/Inputs/rocm/* %t/sysroot/opt/rocm
+// Copy the built clang binary so that its InstalledDir and the real path used
+// by the driver both reside under /opt/rocm/lib/llvm/bin, which is what the
+// detection logic inspects.
+// RUN: mkdir -p %t/sysroot/opt/rocm/lib/llvm/bin
+// RUN: cp %clang %t/sysroot/opt/rocm/lib/llvm/bin/clang
+// RUN: %t/sysroot/opt/rocm/lib/llvm/bin/clang -### --target=x86_64-linux-gnu \
+// RUN:   --offload-arch=gfx1010 --print-rocm-search-dirs %s 2>&1 \
+// RUN:   | FileCheck -check-prefixes=ROCM-LIB-LLVM %s
+//
+// ROCM-LIB-LLVM: ROCm installation search path: {{.*sysroot/opt/rocm$}}
+// ROCM-LIB-LLVM-NOT: ROCm installation search path: {{.*sysroot/opt/rocm/lib$}}