Revert "Add the ability to source RBE related scripts from envsetup.sh"

This reverts commit 9aa9e47b8c.

Reason for revert: DroidMonitor-triggered revert due to breakage https://android-build.googleplex.com/builds/quarterdeck?branch=git_rvc-qpr-dev-plus-aosp&target=ndk&lkgb=7546337&lkbb=7546521&fkbb=7546426, bug https://buganizer.corp.google.com/issues/193566521

Fix: 193566521
Change-Id: I7196a00006499f729baa86a252b0df6535c6aeaa

envsetup.sh

@@ -1871,16 +1871,6 @@ function showcommands() {
     fi
 }
 
-# Source necessary setup scripts needed to run the build with Remote Execution.
-function source_rbe() {
-    local T=$(gettop)
-
-    if [[ "x$USE_RBE" != "x" && "$USE_RBE" != "false" ]]; then
-        . $T/make/rbesetup.sh --skip-envsetup
-    fi
-}
-
 validate_current_shell
 source_vendorsetup
-source_rbe
 addcompletions

rbesetup.sh

@@ -24,11 +24,8 @@ function _source_env_setup_script() {
 }
 
 # This function needs to run first as the remaining defining functions may be
-# using the envsetup.sh defined functions. Skip this part if this script is already
-# being invoked from envsetup.sh.
-if [[ "$1" != "--skip-envsetup" ]]; then
+# using the envsetup.sh defined functions.
 _source_env_setup_script || return
-fi
 
 # This function prefixes the given command with appropriate variables needed
 # for the build to be executed with RBE.