--- a/ext/mbstring/config.m4	2019-12-25 11:16:35.044396365 +0000
+++ b/ext/mbstring/config.m4	2019-12-25 11:05:12.855633553 +0000
@@ -51,7 +51,9 @@
 
 AC_DEFUN([PHP_MBSTRING_SETUP_MBREGEX], [
   if test "$PHP_MBREGEX" = "yes"; then
-    PKG_CHECK_MODULES([ONIG], [oniguruma])
+    if test -z "$ONIG_LIBS" && test -z "$ONIG_CFLAGS"; then
+      PKG_CHECK_MODULES([ONIG], [oniguruma])
+    fi
     PHP_EVAL_LIBLINE($ONIG_LIBS, MBSTRING_SHARED_LIBADD)
     PHP_EVAL_INCLINE($ONIG_CFLAGS)