add: crossystem (#2418)

anda/tools/crossystem/disable-werror.patch

@@ -0,0 +1,13 @@
+diff --git a/Makefile b/Makefile
+index 295b680..2e12cfa 100644
+--- a/Makefile
++++ b/Makefile
+@@ -125,7 +125,7 @@ endif
+ # Provide default CC and CFLAGS for firmware builds; if you have any -D flags,
+ # please add them after this point (e.g., -DVBOOT_DEBUG).
+ DEBUG_FLAGS := $(if $(filter-out 0,${DEBUG}),-g -Og,-g -Os)
+-WERROR := -Werror
++WERROR := -Wno-error
+ FIRMWARE_FLAGS := -nostdinc -ffreestanding -fno-builtin -fno-stack-protector
+ COMMON_FLAGS := -pipe ${WERROR} -Wall -Wstrict-prototypes -Wtype-limits \
+ 	-Wundef -Wmissing-prototypes -Wno-trigraphs -Wredundant-decls -Wshadow \