CMakeLists.txt: For FreeBSD, now looking into /usr/lib in addition to

/usr/local/lib if argp gets moved into the FreeBSD distribution in the
future.

Author: 21M4TW

CMakeLists.txt

@@ -78,7 +78,10 @@ set(ARGP_LIBS "")
 check_function_exists(argp_parse HAVE_ARGP_PARSE)
 if(NOT HAVE_ARGP_PARSE)
 	if(CMAKE_SYSTEM_NAME STREQUAL "FreeBSD")
-		check_library_exists(argp argp_parse "/usr/local/lib" ARGP)
+		find_library(FBSD_ARGP_PATH NAMES argp PATHS "/usr/local/lib" "/usr/lib")
+		if(FBSD_ARGP_PATH)
+			check_library_exists(${FBSD_ARGP_PATH} argp_parse "" ARGP)
+		endif()
 	else()
 		check_library_exists(argp argp_parse "" ARGP)
 	endif()