bibletime: restrict java heap size on 32-bit hosts

this fixes build on ppc-musl at very least, where it fails to
reserve heap memory with the default numbers

srcpkgs/bibletime/template

@@ -21,6 +21,9 @@ checksum=d6beef62ad44b255e3dc4c5e89214bf01a0e85c9136073b0be12fca3d2b22622
 
 pre_build() {
 	. /etc/profile.d/10_openjdk11.sh
+	if [ "$XBPS_WORDSIZE" = "32" ]; then
+		export _JAVA_OPTIONS="-Xmx1024m"
+	fi
 }
 
 pre_check() {