Change approach to make it more configurable

Use GitHub syntax instead

Author: raulcd

dev/release/verify-release-candidate.sh

@@ -512,15 +512,6 @@ test_and_install_cpp() {
     ARROW_BUILD_TESTS=ON
   fi
 
-  case "$(uname)" in
-     Linux)
-      GTest_SOURCE=BUNDLED
-      ;;
-    Darwin)
-      GTest_SOURCE=SYSTEM
-      ;;
-  esac
-
   cmake \
     -DARROW_BOOST_USE_SHARED=ON \
     -DARROW_BUILD_EXAMPLES=OFF \
@@ -557,7 +548,7 @@ test_and_install_cpp() {
     -DCMAKE_INSTALL_LIBDIR=lib \
     -DCMAKE_INSTALL_PREFIX=$ARROW_HOME \
     -DCMAKE_UNITY_BUILD=${CMAKE_UNITY_BUILD:-OFF} \
-    -DGTest_SOURCE=${GTest_SOURCE} \
+    -DGTest_SOURCE=${GTest_SOURCE:-BUNDLED} \
     -DPARQUET_BUILD_EXAMPLES=ON \
     -DPARQUET_BUILD_EXECUTABLES=ON \
     -DPARQUET_REQUIRE_ENCRYPTION=ON \

dev/tasks/verify-rc/github.macos.yml

@@ -89,6 +89,8 @@ jobs:
           PYTHON_VERSION: "3.12"
           {% endif %}
           USE_CONDA: 1
+        {% else %}
+          GTest_SOURCE: SYSTEM
         {% endif %}
         run: |
           arrow/dev/release/verify-release-candidate.sh {{ release|default("") }} {{ rc|default("") }}