toolchain: Update GCC 9 to version 9.3.0

The removed patch is included in GCC 9.3.0.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

toolchain/gcc/patches/9.3.0/851-libgcc_no_compat.patch

@@ -0,0 +1,22 @@
+commit 64661de100da1ec1061ef3e5e400285dce115e6b
+Author: Felix Fietkau <nbd@openwrt.org>
+Date:   Sun May 10 13:16:35 2015 +0000
+
+    gcc: add some size optimization patches
+    
+    Signed-off-by: Felix Fietkau <nbd@openwrt.org>
+    
+    SVN-Revision: 45664
+
+--- a/libgcc/config/t-libunwind
++++ b/libgcc/config/t-libunwind
+@@ -2,8 +2,7 @@
+ 
+ HOST_LIBGCC2_CFLAGS += -DUSE_GAS_SYMVER
+ 
+-LIB2ADDEH = $(srcdir)/unwind-sjlj.c $(srcdir)/unwind-c.c \
+-  $(srcdir)/unwind-compat.c $(srcdir)/unwind-dw2-fde-compat.c
++LIB2ADDEH = $(srcdir)/unwind-sjlj.c $(srcdir)/unwind-c.c
+ LIB2ADDEHSTATIC = $(srcdir)/unwind-sjlj.c $(srcdir)/unwind-c.c
+ 
+ # Override the default value from t-slibgcc-elf-ver and mention -lunwind