Make it possible to reuse built chcache binary

Author: antaljanosbenjamin

CMakeLists.txt

@@ -620,9 +620,10 @@ endif()
 
 include (cmake/sanitize_targets.cmake)
 
-if (COMPILER_CACHE STREQUAL "chcache")
+if (COMPILER_CACHE STREQUAL "chcache" AND CHCACHE_EXECUTABLE_PATH STREQUAL "")
+    message(STATUS "Adding chcache as dependency to all other targets")
     get_all_targets(all_targets)
-    set (chcache_targets _cargo-build_chcache cargo-build_chcache cargo-prebuild_chcache)
+    set(chcache_targets _cargo-build_chcache cargo-build_chcache cargo-prebuild_chcache)
     foreach(target ${all_targets})
         if (target IN_LIST chcache_targets)
             continue()

cmake/ccache.cmake

@@ -2,6 +2,8 @@
 
 include(cmake/utils.cmake)
 
+set(CHCACHE_EXECUTABLE_PATH "" CACHE STRING "Path to chcache executable to use. If the compiler cache is set to use chcache, chcache will be used from here instead of building it.")
+
 # Defensive programming: early return to avoid configuring any cache after we've set dummy launchers.
 # If something includes this file by mistake after the first setup, it'd override the dummy launchers.
 if(USING_DUMMY_LAUNCHERS)
@@ -27,7 +29,13 @@ elseif (COMPILER_CACHE STREQUAL "ccache")
 elseif(COMPILER_CACHE STREQUAL "sccache")
     find_program (CCACHE_EXECUTABLE sccache)
 elseif(COMPILER_CACHE STREQUAL "chcache")
-    set(CCACHE_EXECUTABLE ${CMAKE_CURRENT_BINARY_DIR}/rust/chcache/chcache)
+    if (CHCACHE_EXECUTABLE_PATH STREQUAL "")
+        message(STATUS "Using built chcache")
+        set(CCACHE_EXECUTABLE ${CMAKE_CURRENT_BINARY_DIR}/rust/chcache/chcache)
+    else()
+        message(STATUS "Using chcache from ${CHCACHE_EXECUTABLE_PATH}")
+        set(CCACHE_EXECUTABLE ${CHCACHE_EXECUTABLE_PATH})
+    endif()
 elseif(COMPILER_CACHE STREQUAL "disabled")
     message(STATUS "Using *ccache: no (disabled via configuration)")
     return()