[Libc][AMDGPU] Reduce number of tests for speed up (#308)

This removes the targets check-clang, check-llvm and check-lld from this
bot to give it a little less work and reduce turnaround time. We test
these targets in other bots already.

buildbot/osuosl/master/config/builders.py

@@ -1940,7 +1940,7 @@
                             "-DTEST_SUITE_SOLLVEVV_OFFLOADING_CFLAGS=-fopenmp;-fopenmp-targets=amdgcn-amd-amdhsa;-Xopenmp-target=amdgcn-amd-amdhsa;-march=gfx906",
                             "-DTEST_SUITE_SOLLVEVV_OFFLOADING_LDLAGS=-fopenmp;-fopenmp-targets=amdgcn-amd-amdhsa;-Xopenmp-target=amdgcn-amd-amdhsa;-march=gfx906",
                         ],
-                        add_lit_checks=["check-clang", "check-llvm", "check-lld", "check-offload", "check-libc-amdgcn-amd-amdhsa"]
+                        add_lit_checks=["check-offload", "check-libc-amdgcn-amd-amdhsa"]
                     )},
 
     {'name' : "openmp-offload-amdgpu-clang-flang",