xbps-src: multiple changes to improve infrastructure.

- Remove buildvars_funcs.sh, its code has been moved into set_tmpl_common_vars().
- Move stripping code into its own file, and don't run it via fakeroot.
- Remove unnecesary reset_tmpl_vars() call in install_pkg().
- Misc changes.

xbps-src/shutils/configure_funcs.sh

@@ -84,9 +84,6 @@ configure_src_phase()
 		cd $build_wrksrc || return 1
 	fi
 
-	. $XBPS_SHUTILSDIR/buildvars_funcs.sh
-	set_build_vars
-
 	case "$build_style" in
 	gnu_configure|gnu-configure)
 		#
@@ -141,7 +138,6 @@ configure_src_phase()
 	for f in ${configure_env}; do
 		unset eval ${f%=*}
 	done
-	unset_build_vars
 
 	touch -f $XBPS_CONFIGURE_DONE
 }