add shared patches for GCC8 compatibility

This introduces a new .shared-patches folder. New
"pmbootstrap aportgen" code will make use of this, and create symlinks
to the patches inside that folder when running
"pmbootstrap aportgen linux-..." (or using the new device wizard).

.shared-patches/linux/gcc7-give-up-on-ilog2-const-optimizations.patch

@@ -0,0 +1,90 @@
+From a7bfe0a2832e66f3d732e4210b5d53c81cc7a85f Mon Sep 17 00:00:00 2001
+From: Linus Torvalds <torvalds@linux-foundation.org>
+Date: Thu, 27 Sep 2018 19:16:56 -0400
+Subject: [PATCH] give up on gcc ilog2() constant optimizations
+
+commit 474c90156c8dcc2fa815e6716cc9394d7930cb9c upstream.
+
+gcc-7 has an "optimization" pass that completely screws up, and
+generates the code expansion for the (impossible) case of calling
+ilog2() with a zero constant, even when the code gcc compiles does not
+actually have a zero constant.
+
+And we try to generate a compile-time error for anybody doing ilog2() on
+a constant where that doesn't make sense (be it zero or negative).  So
+now gcc7 will fail the build due to our sanity checking, because it
+created that constant-zero case that didn't actually exist in the source
+code.
+
+There's a whole long discussion on the kernel mailing about how to work
+around this gcc bug.  The gcc people themselevs have discussed their
+"feature" in
+
+   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=72785
+
+but it's all water under the bridge, because while it looked at one
+point like it would be solved by the time gcc7 was released, that was
+not to be.
+
+So now we have to deal with this compiler braindamage.
+
+And the only simple approach seems to be to just delete the code that
+tries to warn about bad uses of ilog2().
+
+So now "ilog2()" will just return 0 not just for the value 1, but for
+any non-positive value too.
+
+It's not like I can recall anybody having ever actually tried to use
+this function on any invalid value, but maybe the sanity check just
+meant that such code never made it out in public.
+
+[js] no tools/include/linux/log2.h copy of that yet
+
+Reported-by: Laura Abbott <labbott@redhat.com>
+Cc: John Stultz <john.stultz@linaro.org>,
+Cc: Thomas Gleixner <tglx@linutronix.de>
+Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
+Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
+Signed-off-by: Jiri Slaby <jslaby@suse.cz>
+---
+ include/linux/log2.h | 13 ++-----------
+ 1 file changed, 2 insertions(+), 11 deletions(-)
+
+diff --git a/include/linux/log2.h b/include/linux/log2.h
+index fd7ff3d91..f38fae23b 100644
+--- a/include/linux/log2.h
++++ b/include/linux/log2.h
+@@ -15,12 +15,6 @@
+ #include <linux/types.h>
+ #include <linux/bitops.h>
+ 
+-/*
+- * deal with unrepresentable constant logarithms
+- */
+-extern __attribute__((const, noreturn))
+-int ____ilog2_NaN(void);
+-
+ /*
+  * non-constant log of base 2 calculators
+  * - the arch may override these in asm/bitops.h if they can be implemented
+@@ -85,7 +79,7 @@ unsigned long __rounddown_pow_of_two(unsigned long n)
+ #define ilog2(n)				\
+ (						\
+ 	__builtin_constant_p(n) ? (		\
+-		(n) < 1 ? ____ilog2_NaN() :	\
++		(n) < 2 ? 0 :			\
+ 		(n) & (1ULL << 63) ? 63 :	\
+ 		(n) & (1ULL << 62) ? 62 :	\
+ 		(n) & (1ULL << 61) ? 61 :	\
+@@ -148,10 +142,7 @@ unsigned long __rounddown_pow_of_two(unsigned long n)
+ 		(n) & (1ULL <<  4) ?  4 :	\
+ 		(n) & (1ULL <<  3) ?  3 :	\
+ 		(n) & (1ULL <<  2) ?  2 :	\
+-		(n) & (1ULL <<  1) ?  1 :	\
+-		(n) & (1ULL <<  0) ?  0 :	\
+-		____ilog2_NaN()			\
+-				   ) :		\
++		1 ) :				\
+ 	(sizeof(n) <= 4) ?			\
+ 	__ilog2_u32(n) :			\
+ 	__ilog2_u64(n)				\

.shared-patches/linux/gcc8-fix-put-user.patch

@@ -0,0 +1,45 @@
+From 8c8187d41b99acd4f2078d0fff6807e0eeb47407 Mon Sep 17 00:00:00 2001
+From: Arnd Bergmann <arnd@arndb.de>
+Date: Thu, 26 Jul 2018 10:13:23 +0200
+Subject: [PATCH] ARM: fix put_user() for gcc-8
+
+Building kernels before linux-4.7 with gcc-8 results in many build failures
+when gcc triggers a check that was meant to catch broken compilers:
+
+/tmp/ccCGMQmS.s:648: Error: .err encountered
+
+According to the discussion in the gcc bugzilla, a local "register
+asm()" variable is still supposed to be the correct way to force an
+inline assembly to use a particular register, but marking it 'const'
+lets the compiler do optimizations that break that, i.e the compiler is
+free to treat the variable as either 'const' or 'register' in that case.
+
+Upstream commit 9f73bd8bb445 ("ARM: uaccess: remove put_user() code
+duplication") fixed this problem in linux-4.8 as part of a larger change,
+but seems a little too big to be backported to 4.4.
+
+Let's take the simplest fix and change only the one broken line in the
+same way as newer kernels.
+
+Suggested-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
+Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85745
+Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86673
+Signed-off-by: Arnd Bergmann <arnd@arndb.de>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ arch/arm/include/asm/uaccess.h | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h
+index 292c3f88f..48decaa00 100644
+--- a/arch/arm/include/asm/uaccess.h
++++ b/arch/arm/include/asm/uaccess.h
+@@ -158,7 +158,7 @@ extern int __put_user_8(void *, unsigned long long);
+ #define put_user(x,p)							\
+ 	({								\
+ 		unsigned long __limit = current_thread_info()->addr_limit - 1; \
+-		register const typeof(*(p)) __r2 asm("r2") = (x);	\
++		register typeof(*(p)) __r2 asm("r2") = (x);	\
+ 		register const typeof(*(p)) __user *__p asm("r0") = (p);\
+ 		register unsigned long __l asm("r1") = __limit;		\
+ 		register int __e asm("r0");				\