gdb: bump to 7.8.1

This commit bumps to 7.8.1, and updates the logic to use .tar.xz
tarballs so that it applies to all 7.8.x versions.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/gdb/Config.in.host

@@ -55,4 +55,4 @@ config BR2_GDB_VERSION
 	default "arc-2014.08-gdb" if BR2_arc
 	default "6be65fb56ea6694a9260733a536a023a1e2d4d57" if BR2_microblaze
 	default "7.7.1"    if BR2_GDB_VERSION_7_7 || !BR2_PACKAGE_HOST_GDB
-	default "7.8"	   if BR2_GDB_VERSION_7_8
+	default "7.8.1"	   if BR2_GDB_VERSION_7_8

package/gdb/gdb.mk

@@ -23,7 +23,9 @@ ifeq ($(GDB_VERSION),6.7.1-avr32-2.1.5)
 GDB_SITE = ftp://www.at91.com/pub/buildroot
 endif
 
-ifeq ($(GDB_VERSION),7.8)
+# Starting from 7.8.x, bz2 tarballs no longer available, use .tar.xz
+# instead.
+ifneq ($(filter 7.8.%,$(GDB_VERSION)),)
 GDB_SOURCE = gdb-$(GDB_VERSION).tar.xz
 endif