Change depot_tools' PATH precedence to last

Otherwise building WebRTC explodes in python3 processes.

On Ubuntu 22 vpython3 is required in PATH, so depot_tools cannot be
omitted.

Library/TeamTalkLib/build/webrtc/CMakeLists.txt

@@ -215,7 +215,7 @@ else()
       )
     ExternalProject_Get_Property(depot-tools SOURCE_DIR)
     set (DEPOTTOOLS_DIR ${SOURCE_DIR})
-    set (DEPOTTOOLS_EXPORT export PATH=${DEPOTTOOLS_DIR}:$ENV{PATH} OPENSSL_DIR=${OPENSSL_DIR})
+    set (DEPOTTOOLS_EXPORT export PATH=$ENV{PATH}:${DEPOTTOOLS_DIR} OPENSSL_DIR=${OPENSSL_DIR})
 
     if (${CMAKE_SYSTEM_NAME} MATCHES "iOS")
       set (WEBRTC_REPO_NAME webrtc_ios)