chore: Use mold when available without option (#2521)

Author: mathbunnyru

.github/actions/cmake/action.yml

@@ -33,10 +33,6 @@ inputs:
     description: Whether to enable compiler trace reports
     required: true
     default: "false"
-  use_mold:
-    description: Whether to use mold linker
-    required: true
-    default: "false"
   package:
     description: Whether to generate Debian package
     required: true
@@ -59,7 +55,6 @@ runs:
         COVERAGE: "${{ inputs.code_coverage == 'true' && 'ON' || 'OFF' }}"
         STATIC: "${{ inputs.static == 'true' && 'ON' || 'OFF' }}"
         TIME_TRACE: "${{ inputs.time_trace == 'true' && 'ON' || 'OFF' }}"
-        USE_MOLD: "${{ inputs.use_mold == 'true' && 'ON' || 'OFF' }}"
         PACKAGE: "${{ inputs.package == 'true' && 'ON' || 'OFF' }}"
       run: |
         cmake \
@@ -74,5 +69,4 @@ runs:
           -Dcoverage="${COVERAGE}" \
           -Dstatic="${STATIC}" \
           -Dtime_trace="${TIME_TRACE}" \
-          -Duse_mold="${USE_MOLD}" \
           -Dpackage="${PACKAGE}"

.github/workflows/build_impl.yml

@@ -121,7 +121,6 @@ jobs:
           code_coverage: ${{ inputs.code_coverage }}
           static: ${{ inputs.static }}
           time_trace: ${{ inputs.analyze_build_time }}
-          use_mold: ${{ runner.os != 'macOS' }}
           package: ${{ inputs.package }}
 
       - name: Build Clio

CMakeLists.txt

@@ -16,7 +16,6 @@ option(lint "Run clang-tidy checks during compilation" FALSE)
 option(static "Statically linked Clio" FALSE)
 option(snapshot "Build snapshot tool" FALSE)
 option(time_trace "Build using -ftime-trace to create compiler trace reports" FALSE)
-option(use_mold "Use mold linker" FALSE)
 
 # ========================================================================== #
 set(san "" CACHE STRING "Add sanitizer instrumentation")

cmake/Linker.cmake

@@ -1,8 +1,11 @@
-if (use_mold)
-  if (CMAKE_SYSTEM_NAME STREQUAL "Linux")
-    message(STATUS "Using Mold linker")
-    set(CMAKE_LINKER_TYPE MOLD)
-  else ()
-    message(FATAL_ERROR "Mold linker is only supported on Linux.")
-  endif ()
+if (DEFINED CMAKE_LINKER_TYPE)
+  message(STATUS "Custom linker is already set: ${CMAKE_LINKER_TYPE}")
+  return()
+endif ()
+
+find_program(MOLD_PATH mold)
+
+if (MOLD_PATH AND CMAKE_SYSTEM_NAME STREQUAL "Linux")
+  message(STATUS "Using Mold linker: ${MOLD_PATH}")
+  set(CMAKE_LINKER_TYPE MOLD)
 endif ()