set search path args and then append (#543)

Fix appending search paths specified by GTEST_DIR that was being
overridden by the set command for system paths

Signed-off-by: William Wedler <[email protected]>
Co-authored-by: William Wedler <[email protected]>

Author: zflat

ament_cmake_gtest/ament_cmake_gtest-extras.cmake

@@ -24,19 +24,16 @@ macro(_ament_cmake_gtest_find_gtest)
     # if gtest sources were not found in a previous run
     if(NOT GTEST_FROM_SOURCE_FOUND)
       # search path for gtest includes and sources
-      set(_search_path_include "")
-      set(_search_path_src "")
+      # check the system installed path (i.e. on Ubuntu)
+      set(_search_path_include "/usr/include/gtest")
+      set(_search_path_src "/usr/src/gtest/src")
 
       # option() consider environment variable to find gtest
       if(NOT $ENV{GTEST_DIR} STREQUAL "")
         list(APPEND _search_path_include "$ENV{GTEST_DIR}/include/gtest")
         list(APPEND _search_path_src "$ENV{GTEST_DIR}/src")
       endif()
 
-      # check to system installed path (i.e. on Ubuntu)
-      set(_search_path_include "/usr/include/gtest")
-      set(_search_path_src "/usr/src/gtest/src")
-
       # check gtest_vendor path, prefer this version over a system installed
       find_package(gtest_vendor QUIET)
       if(gtest_vendor_FOUND AND gtest_vendor_BASE_DIR)