Allow Lit to use 'ptxas' tool to validate generated PTX on the NVPTX builders. (#390)

Specify LLVM_PTXAS_EXECUTABLE environment variable with a full path to
'ptxas' tool from installed NVIDIA CUDA Toolkit. LIT will be
automatically check and use this tool to validate PTX during the tests.

Author: vvereschaka

buildbot/osuosl/master/config/builders.py

@@ -3103,6 +3103,8 @@
                         # TMP/TEMP within the build dir (to utilize a ramdisk).
                         'TMP'        : util.Interpolate("%(prop:builddir)s/build"),
                         'TEMP'       : util.Interpolate("%(prop:builddir)s/build"),
+                        # Allow Lit to use 'ptxas' tool to validate generated PTX.
+                        'LLVM_PTXAS_EXECUTABLE' : "/usr/local/cuda/bin/ptxas",
                     })},
 
     {'name' : "llvm-nvptx64-nvidia-ubuntu",
@@ -3128,6 +3130,8 @@
                         # TMP/TEMP within the build dir (to utilize a ramdisk).
                         'TMP'        : util.Interpolate("%(prop:builddir)s/build"),
                         'TEMP'       : util.Interpolate("%(prop:builddir)s/build"),
+                        # Allow Lit to use 'ptxas' tool to validate generated PTX.
+                        'LLVM_PTXAS_EXECUTABLE' : "/usr/local/cuda/bin/ptxas",
                     })},
 
     {'name' : "llvm-nvptx-nvidia-win",
@@ -3151,6 +3155,8 @@
                         # TMP/TEMP within the build dir (to utilize a ramdisk).
                         'TMP'        : util.Interpolate("%(prop:builddir)s/build"),
                         'TEMP'       : util.Interpolate("%(prop:builddir)s/build"),
+                        # Allow Lit to use 'ptxas' tool to validate generated PTX.
+                        'LLVM_PTXAS_EXECUTABLE' : "c:/buildbot/latest-cuda/bin/ptxas.exe",
                     })},
 
     {'name' : "llvm-nvptx64-nvidia-win",
@@ -3174,6 +3180,8 @@
                         # TMP/TEMP within the build dir (to utilize a ramdisk).
                         'TMP'        : util.Interpolate("%(prop:builddir)s/build"),
                         'TEMP'       : util.Interpolate("%(prop:builddir)s/build"),
+                        # Allow Lit to use 'ptxas' tool to validate generated PTX.
+                        'LLVM_PTXAS_EXECUTABLE' : "c:/buildbot/latest-cuda/bin/ptxas.exe",
                     })},
 
     # flang FortranRuntime CUDA Offload builders.