Revert "Build - also remove external/build dir when cleaning"

This reverts commit 16dec61.

(The external/build dir is no longer created as part of the cmake process - I just happened to oddly have an old one hanging around)

Author: samaaron

app/linux-clean.sh

@@ -7,9 +7,6 @@ cd "${SCRIPT_DIR}"
 echo "Cleaning out build dir...."
 rm -rf build
 
-echo "Cleaning out external build dir..."
-rm -rf external/build
-
 echo "Cleaning out BEAM distribution..."
 rm -rf server/beam/tau/_build
 rm -f server/beam/tau/priv/*.{so,dylib,dll}

app/win-clean.bat

@@ -5,9 +5,6 @@ cd %~dp0
 @echo Cleaning out build dir....
 rmdir build /s /q
 
-@echo Cleaning out external build dir....
-rmdir external\build /s /q
-
 @echo Cleaning out BEAM distribution....
 rmdir server\beam\tau\_build /s /q
 del server\beam\tau\priv\*.so server\beam\tau\priv\*.dylib server\beam\tau\priv\*.dll /s /q