Avoid hard coded icu4c path (#11410)

Summary: Pull Request resolved: #11410

Reviewed By: xiaoxmeng, kgpai

Differential Revision: D65354548

Pulled By: tanjialiang

fbshipit-source-id: bd6d4880198bee7162adf84b9e0ee8f8b1dd605d

CMakeLists.txt

@@ -387,7 +387,18 @@ set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
 if(CMAKE_SYSTEM_NAME MATCHES "Darwin")
   if(ON_APPLE_M1)
-    list(APPEND CMAKE_PREFIX_PATH "/opt/homebrew/opt/icu4c")
+    execute_process(
+      COMMAND brew --prefix icu4c
+      RESULT_VARIABLE BREW_ICU4C
+      OUTPUT_VARIABLE BREW_ICU4C_PREFIX
+      OUTPUT_STRIP_TRAILING_WHITESPACE)
+    if(BREW_ICU4C EQUAL 0 AND EXISTS "${BREW_ICU4C_PREFIX}")
+      message(
+        STATUS "Found icu4c installed by Homebrew at ${BREW_ICU4C_PREFIX}")
+      list(APPEND CMAKE_PREFIX_PATH "${BREW_ICU4C_PREFIX}")
+    else()
+      list(APPEND CMAKE_PREFIX_PATH "/usr/local/opt/icu4c")
+    endif()
   else()
     list(APPEND CMAKE_PREFIX_PATH "/usr/local/opt/icu4c")
   endif()