treewide: add ORIG_PATH variable

Add a variable that stores the original value of $PATH
in the host system's shell, before Make alters it.

This can be useful for when it is necessary
to ignore symlinks and programs made by the build system.

Define this new variable before all instances of
'export PATH:=' or similar.

Signed-off-by: Michael Pratt <mcpratt@pm.me>
(cherry picked from commit d87a8aa148)

target/toolchain/files/wrapper.sh

@@ -43,6 +43,7 @@ TOOLCHAIN_BIN_DIR="$REALNAME_DIR/"
 
 # Set the PATH so that our run-time location is first
 # (get_feature is run from the path, so this has to be set)
+export ORIG_PATH=${ORIG_PATH:-$PATH}
 export PATH="$TOOLCHAIN_BIN_DIR":$PATH
 export GCC_HONOUR_COPTS