update gcc7 plugin to 7.2.0

plugins/gcc7/gcc7-overlay.mk

@@ -17,8 +17,8 @@ $(PKG)_URL      := http://isl.gforge.inria.fr/$($(PKG)_FILE)
 $(PKG)_URL_2    := ftp://gcc.gnu.org/pub/gcc/infrastructure/$($(PKG)_FILE)
 
 PKG             := gcc
-$(PKG)_VERSION  := 7.1.0
-$(PKG)_CHECKSUM := 8a8136c235f64c6fef69cac0d73a46a1a09bb250776a050aec8f9fc880bebc17
+$(PKG)_VERSION  := 7.2.0
+$(PKG)_CHECKSUM := 1cf7adf8ff4b5aa49041c8734bbcf1ad18cc4c94d0029aae0f4e48841088479a
 $(PKG)_SUBDIR   := gcc-$($(PKG)_VERSION)
-$(PKG)_FILE     := gcc-$($(PKG)_VERSION).tar.bz2
+$(PKG)_FILE     := gcc-$($(PKG)_VERSION).tar.xz
 $(PKG)_URL      := https://ftp.gnu.org/gnu/gcc/gcc-$($(PKG)_VERSION)/$($(PKG)_FILE)