handle errors on exits from subshells

most of these are probably redundant, and will never
be called, but lbmk needs to be as safe as possible
under fault conditions. fail early, fail hard.

Signed-off-by: Leah Rowe <leah@libreboot.org>

script/update/trees

@@ -61,7 +61,7 @@ build_projects()
 		x_ cd src/uefitool
 		cmake UEFIExtract/ || [ -f Makefile ] || \
 		    err "build_projects: !cmake UEFIExtract/"
-	)
+	) || err "can't build cmake on uefiextract"
 	fi
 
 	[ "${mode}" = "distclean" ] && mode="clean"