[appveyor] enable clcache

appveyor.yml

@@ -23,6 +23,9 @@ skip_commits:
 # Add [av skip] to commit messages
   message: /\[av skip\]/
 
+cache:
+  - '%USERPROFILE%\clcache'
+
 environment:
   matrix:
     - COMPILER: clang-cl
@@ -39,8 +42,11 @@ install:
 before_build:
   - echo Running cmake...
   - cd c:\projects\OpenBLAS
+  - ps: If ($env:COMPILER -eq "clang-cl") { $env:PATH = "C:\Python36-x64;C:\Python36-x64\Scripts;$env:PATH;" }
+  - ps: If ($env:COMPILER -eq "clang-cl") { $env:CLCACHE_CL = "clang-cl" }
+  - ps: If ($env:COMPILER -eq "clang-cl") { pip install git+https://github.com/frerich/clcache.git }
   - if [%COMPILER%]==[cl] cmake -G "Visual Studio 12 Win64" .
-  - if [%COMPILER%]==[clang-cl] cmake -G "Ninja" -DCMAKE_CXX_COMPILER=clang-cl -DCMAKE_C_COMPILER=clang-cl .
+  - if [%COMPILER%]==[clang-cl] cmake -G "Ninja" -DCMAKE_CXX_COMPILER=clcache -DCMAKE_C_COMPILER=clcache .
   - if [%DYNAMIC_ARCH%]==[ON] cmake -DDYNAMIC_ARCH=ON .
 
 build_script: