MFC r279598:

When compiling boot2 with gcc on i386 and pc98, only use the custom flag
-mno-align-long-strings when compiling with base gcc. This is checked
by comparing the version number against 4.2.1, which is not exactly
right, but good enough. (There is no other way to check whether we are
using the non-standard gcc in base, as far as I know.)

Reported by: rodrigc