[build-script] Pass LLDB_EXTRA_CMAKE_ARGS last

Pass LLDB_EXTRA_CMAKE_ARGS last so it can override defaults values set
earlier. It also makes sure we only pass LLDB_USE_SYSTEM_DEBUGSERVER
when the corresponding build-script flag is set.

Author: JDevlieghere

utils/build-script-impl

@@ -2439,13 +2439,6 @@ for host in "${ALL_HOSTS[@]}"; do
                     "${lldb_cmake_options[@]}"
                     )
 
-                if [ ! -z "${LLDB_EXTRA_CMAKE_ARGS}" ]; then
-                    cmake_options=(
-                        "${cmake_options[@]}"
-                        ${LLDB_EXTRA_CMAKE_ARGS}
-                        )
-                fi
-
                 # Figure out if we think this is a buildbot build.
                 # This will influence the lldb version line.
                 if [ ! -z "${JENKINS_HOME}" -a ! -z "${JOB_NAME}" -a ! -z "${BUILD_NUMBER}" ]; then
@@ -2518,11 +2511,20 @@ for host in "${ALL_HOSTS[@]}"; do
                     -DLLDB_TEST_USER_ARGS="${DOTEST_ARGS}"
                 )
 
-                if [[ "$(uname -s)" == "Darwin" ]] ; then
+                if [[ "$(uname -s)" == "Darwin" && "$(true_false ${LLDB_USE_SYSTEM_DEBUGSERVER})" == "TRUE" ]]; then
                   cmake_options+=(
                     -DLLDB_USE_SYSTEM_DEBUGSERVER:BOOL="${LLDB_USE_SYSTEM_DEBUGSERVER}"
                   )
                 fi
+
+                # Add the extra CMake args at the end so they can override
+                # values set earlier.
+                if [ ! -z "${LLDB_EXTRA_CMAKE_ARGS}" ]; then
+                    cmake_options=(
+                        "${cmake_options[@]}"
+                        ${LLDB_EXTRA_CMAKE_ARGS}
+                        )
+                fi
                 ;;
             llbuild)
                 cmake_options=(