Reduce binary sizes for the kernel and userspace apps

mk/arch/toolchain-x86_64.mk

@@ -2,4 +2,4 @@ PREFIX := $(ROOT)/toolchain/root/bin
 
 CC := $(PREFIX)/x86_64-elf-gcc
 LD := $(PREFIX)/x86_64-elf-ld
-AR := $(PREFIX)/x86_64-elf-ar
+AR := $(PREFIX)/x86_64-elf-gcc-ar

mk/user/x86_64.mk

@@ -13,4 +13,8 @@ CFLAGS += -m64 \
 					-fno-strict-aliasing \
 					-O0 \
 					-mno-tls-direct-seg-refs \
-					# -fsanitize=undefined
+					-fdata-sections \
+					-ffunction-sections \
+
+LDFLAGS += --gc-sections \
+					 --strip-all