Allow MAKE='make V=1' and similar.

https://bugs.gentoo.org/795678
--- a/configure
+++ b/configure
@@ -1953,7 +1953,7 @@ if test -z "$python"
 then
     error_exit "Python not found. Use --python=/path/to/python"
 fi
-if ! has "$make"
+if ! has $make
 then
     error_exit "GNU make ($make) not found"
 fi