Make -Wcast-align only a warning

On x86 and x86_64, this warning is never emitted because it is perfectly
fine to do unaligned access. On sparc, such accesses are not supported
by the hardware and will generate a SIGBUS. This must be caught by a
trap handler, and the unaligned access performed there, slowly, using
byte by byte access.

However, making this a Werror is annoying because it will trigger
everytime one casts a byte pointer to something larger, even when
alignment is actually preserved. So, removing all such warnings would be
nearly impossible (for example, just for the mergesort function, there
is a whole GSoC project for it at FreeBSD).

Keep it as a warning for now. The warning can be silenced by using
BytePointer, if desired. We should also investigate where the SIGBUS
trap is triggered a lot and consider improving the alignment of data
where possible.

Change-Id: I6b90025e8c6d69ef1ccda3c10eee270ccc1ebd29
Reviewed-on: https://review.haiku-os.org/c/1103
Reviewed-by: waddlesplash <waddlesplash@gmail.com>

build/jam/ArchitectureRules

@@ -115,12 +115,14 @@ rule ArchitectureSetup architecture
 	# warning flags
 	HAIKU_WARNING_CCFLAGS_$(architecture) = -Wall
 		-Wno-multichar
-		-Wpointer-arith -Wcast-align -Wsign-compare
-		-Wmissing-prototypes ;
+		-Wpointer-arith -Wsign-compare
+		-Wmissing-prototypes 
+		-Wcast-align -Wno-error=cast-align ;
 	HAIKU_WARNING_C++FLAGS_$(architecture) = -Wall
 		-Wno-multichar
-		-Wpointer-arith -Wcast-align -Wsign-compare
-		-Wno-ctor-dtor-privacy -Woverloaded-virtual ;
+		-Wpointer-arith -Wsign-compare
+		-Wno-ctor-dtor-privacy -Woverloaded-virtual
+		-Wcast-align -Wno-error=cast-align ;
 
 	# disable some Clang warnings that are not very useful
 	if $(HAIKU_CC_IS_CLANG_$(architecture)) = 1 {