[clang] [clang][OpenMP][test] Use `-fopenmp=libomp` explicitly (PR #180221)

[Jordan Rupprecht via cfe-commits]

https://github.com/rupprecht created https://github.com/llvm/llvm-project/pull/180221

Using `-fopenmp` uses the default openmp lib, which defaults to `libomp` but may be something else. This test only passes with `libomp`, so it passes when using all defaults, but fails downstream if configured for something else, like `libgomp`.

>From ddaf5163c65d2e42cf5292ad851f4305504fe0c6 Mon Sep 17 00:00:00 2001
From: Jordan Rupprecht <rupprecht at google.com>
Date: Fri, 6 Feb 2026 08:07:26 -0800
Subject: [PATCH] use libomp explicitly

---
 clang/test/Driver/openmp-target-fast-flag.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/clang/test/Driver/openmp-target-fast-flag.c b/clang/test/Driver/openmp-target-fast-flag.c
index 4ded4be341801..0390790b3f533 100644
--- a/clang/test/Driver/openmp-target-fast-flag.c
+++ b/clang/test/Driver/openmp-target-fast-flag.c
@@ -1,24 +1,24 @@
 // REQUIRES: x86-registered-target, amdgpu-registered-target
 
-// RUN:   %clang -### -fopenmp -fopenmp-targets=amdgcn-amd-amdhsa -Xopenmp-target=amdgcn-amd-amdhsa -march=gfx90a -nogpulib %s -O0 2>&1 \
+// RUN:   %clang -### -fopenmp=libomp -fopenmp-targets=amdgcn-amd-amdhsa -Xopenmp-target=amdgcn-amd-amdhsa -march=gfx90a -nogpulib %s -O0 2>&1 \
 // RUN:   | FileCheck -check-prefixes=DefaultTFast,DefaultTState,DefaultNoNestParallel %s
 
-// RUN:   %clang -### -fopenmp -fopenmp-targets=amdgcn-amd-amdhsa -Xopenmp-target=amdgcn-amd-amdhsa -march=gfx90a -nogpulib -O0 -fopenmp-target-fast %s 2>&1 \
+// RUN:   %clang -### -fopenmp=libomp -fopenmp-targets=amdgcn-amd-amdhsa -Xopenmp-target=amdgcn-amd-amdhsa -march=gfx90a -nogpulib -O0 -fopenmp-target-fast %s 2>&1 \
 // RUN:   | FileCheck -check-prefixes=TState,NestParallel %s
 
-// RUN:   %clang -### -fopenmp -fopenmp-targets=amdgcn-amd-amdhsa -Xopenmp-target=amdgcn-amd-amdhsa -march=gfx90a -nogpulib -O3 %s 2>&1 \
+// RUN:   %clang -### -fopenmp=libomp -fopenmp-targets=amdgcn-amd-amdhsa -Xopenmp-target=amdgcn-amd-amdhsa -march=gfx90a -nogpulib -O3 %s 2>&1 \
 // RUN:   | FileCheck -check-prefixes=O3,DefaultTFast,DefaultTState,DefaultNoNestParallel %s
 
-// RUN:   %clang -### -fopenmp -fopenmp-targets=amdgcn-amd-amdhsa -Xopenmp-target=amdgcn-amd-amdhsa -march=gfx90a -nogpulib -O3 -fno-openmp-target-fast %s 2>&1 \
+// RUN:   %clang -### -fopenmp=libomp -fopenmp-targets=amdgcn-amd-amdhsa -Xopenmp-target=amdgcn-amd-amdhsa -march=gfx90a -nogpulib -O3 -fno-openmp-target-fast %s 2>&1 \
 // RUN:   | FileCheck -check-prefixes=O3,DefaultTState,DefaultNoNestParallel %s
 
-// RUN:   %clang -### -fopenmp -fopenmp-targets=amdgcn-amd-amdhsa -Xopenmp-target=amdgcn-amd-amdhsa -march=gfx90a -nogpulib -Ofast %s 2>&1 \
+// RUN:   %clang -### -fopenmp=libomp -fopenmp-targets=amdgcn-amd-amdhsa -Xopenmp-target=amdgcn-amd-amdhsa -march=gfx90a -nogpulib -Ofast %s 2>&1 \
 // RUN:   | FileCheck -check-prefixes=OFast,TState,NestParallel %s
 
-// RUN:   %clang -### -fopenmp -fopenmp-targets=amdgcn-amd-amdhsa -Xopenmp-target=amdgcn-amd-amdhsa -march=gfx90a -nogpulib -Ofast -fno-openmp-target-fast %s 2>&1 \
+// RUN:   %clang -### -fopenmp=libomp -fopenmp-targets=amdgcn-amd-amdhsa -Xopenmp-target=amdgcn-amd-amdhsa -march=gfx90a -nogpulib -Ofast -fno-openmp-target-fast %s 2>&1 \
 // RUN:   | FileCheck -check-prefixes=OFast,DefaultTState,DefaultNoNestParallel %s
 
-// RUN:   %clang -### -fopenmp -fopenmp-targets=amdgcn-amd-amdhsa -Xopenmp-target=amdgcn-amd-amdhsa -march=gfx90a -nogpulib -O0 -fno-openmp-target-fast -fopenmp-target-fast %s 2>&1 \
+// RUN:   %clang -### -fopenmp=libomp -fopenmp-targets=amdgcn-amd-amdhsa -Xopenmp-target=amdgcn-amd-amdhsa -march=gfx90a -nogpulib -O0 -fno-openmp-target-fast -fopenmp-target-fast %s 2>&1 \
 // RUN:   | FileCheck -check-prefixes=TState,NestParallel %s
 
 // O3: -O3