https://bugzilla.mozilla.org/show_bug.cgi?id=1391072

diff -r 883bf2620473 -r 7ab6305b7f40 build/autoconf/config.guess
--- firefox-100.0/build/autoconf/config.guess.old	2022-04-14 14:03:22.196794369 +0000
+++ firefox-100.0/build/autoconf/config.guess	2022-04-14 14:04:53.147103647 +0000
@@ -424,7 +424,7 @@
 	;;
     sun4*:SunOS:5.*:* | tadpole*:SunOS:5.*:*)
 	SUN_REL=`echo "$UNAME_RELEASE" | sed -e 's/[^.]*//'`
-	GUESS=sparc-sun-solaris2$SUN_REL
+	GUESS=sparc64-sun-solaris2$SUN_REL
 	;;
     i86pc:AuroraUX:5.*:* | i86xen:AuroraUX:5.*:*)
 	GUESS=i386-pc-auroraux$UNAME_RELEASE