8249255: Build fails if source code in cygwin home dir

Reviewed-by: tbell

Author: erikj79

make/autoconf/basic.m4

@@ -86,17 +86,18 @@ AC_DEFUN_ONCE([BASIC_SETUP_PATHS],
   AC_SUBST(TOPDIR)
   AC_SUBST(CONFIGURE_START_DIR)
 
+  # We can only call UTIL_FIXUP_PATH after BASIC_CHECK_PATHS_WINDOWS.
+  UTIL_FIXUP_PATH(TOPDIR)
+  UTIL_FIXUP_PATH(CONFIGURE_START_DIR)
+
   if test "x$CUSTOM_ROOT" != x; then
+    UTIL_FIXUP_PATH(CUSTOM_ROOT)
     WORKSPACE_ROOT="${CUSTOM_ROOT}"
   else
     WORKSPACE_ROOT="${TOPDIR}"
   fi
   AC_SUBST(WORKSPACE_ROOT)
 
-  # We can only call UTIL_FIXUP_PATH after BASIC_CHECK_PATHS_WINDOWS.
-  UTIL_FIXUP_PATH(CONFIGURE_START_DIR)
-  UTIL_FIXUP_PATH(TOPDIR)
-
   # Locate the directory of this script.
   AUTOCONF_DIR=$TOPDIR/make/autoconf