message: build: consistently quote AC_CHECK_PROG() arguments
diff: @@ -673,7 +673,7 @@ case $host in
  if test x$cross_compiling != xyes; then
  BUILD_OS=darwin
  AC_PATH_PROGS([RSVG_CONVERT], [rsvg-convert rsvg], [rsvg-convert])
  - AC_CHECK_PROG([BREW],brew, brew)
  + AC_CHECK_PROG([BREW], [brew], [brew])
  if test x$BREW = xbrew; then
  dnl These Homebrew packages may be keg-only, meaning that they won't be found
  dnl in expected paths because they may conflict with system files. Ask
  