Add ICU_ROOT environment variable support to fix macOS build with Homebrew ICU

Author: sosukesuzuki

.github/workflows/build-reusable.yml

@@ -104,6 +104,7 @@ jobs:
       - name: Run
         env:
           ICU_INCLUDE_DIRS: ${{matrix.brew_prefix}}/icu4c/include
+          ICU_ROOT: ${{matrix.brew_prefix}}/icu4c
           LDFLAGS: "${{env.LDFLAGS}} "
           CC: "${{matrix.brew_prefix}}/llvm@${{env.LLVM_VERSION}}/bin/clang"
           CXX: "${{matrix.brew_prefix}}/llvm@${{env.LLVM_VERSION}}/bin/clang++"

Source/cmake/OptionsJSCOnly.cmake

@@ -209,6 +209,10 @@ if (DEFINED ENV{ICU_INCLUDE_DIRS})
     set(ICU_INCLUDE_DIRS "$ENV{ICU_INCLUDE_DIRS}" CACHE "" INTERNAL FORCE)
 endif ()
 
+if (DEFINED ENV{ICU_ROOT})
+    set(ICU_ROOT "$ENV{ICU_ROOT}" CACHE PATH "" FORCE)
+endif ()
+
 find_package(ICU 70.1 REQUIRED COMPONENTS data i18n uc)
 
 if (APPLE)