set CMAKE_HIP_COMPILER_LAUNCHER env var, not cmake var

Author: Olivier Chafik

.github/workflows/build.yml

@@ -1186,6 +1186,7 @@ jobs:
         run: |
           $env:HIP_PATH=$(Resolve-Path 'C:\Program Files\AMD\ROCm\*\bin\clang.exe' | split-path | split-path)
           $env:CMAKE_PREFIX_PATH="${env:HIP_PATH}"
+          $env:CMAKE_HIP_COMPILER_LAUNCHER=sccache
           cmake -G "Unix Makefiles" -B build -S . `
             -DCMAKE_C_COMPILER="${env:HIP_PATH}\bin\clang.exe" `
             -DCMAKE_CXX_COMPILER="${env:HIP_PATH}\bin\clang++.exe" `
@@ -1236,6 +1237,7 @@ jobs:
         run: |
           $env:HIP_PATH=$(Resolve-Path 'C:\Program Files\AMD\ROCm\*\bin\clang.exe' | split-path | split-path)
           $env:CMAKE_PREFIX_PATH="${env:HIP_PATH}"
+          $env:CMAKE_HIP_COMPILER_LAUNCHER=sccache
           cmake -G "Unix Makefiles" -B build -S . `
             -DCMAKE_C_COMPILER="${env:HIP_PATH}\bin\clang.exe" `
             -DCMAKE_CXX_COMPILER="${env:HIP_PATH}\bin\clang++.exe" `

ggml/src/CMakeLists.txt

@@ -100,10 +100,6 @@ if (GGML_CCACHE)
             set(GGML_CCACHE_VARIANT ccache)
         else()
             set(GGML_CCACHE_VARIANT sccache)
-            if(GGML_HIP)
-                # TODO: should not be set globally
-                set(GLOBAL CMAKE_HIP_COMPILER_LAUNCHER sccache)
-            endif()
         endif()
         # TODO: should not be set globally
         set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE "${GGML_CCACHE_VARIANT}")