Use -O3 build optimization flag for base and BORE kernels

Signed-off-by: Krzysztof Wilczyński <kwilczynski@omarchy.org>

pkgbuilds/linux-omarchy/0011-kbuild-optimize-for-performance-o3.patch

@@ -0,0 +1,31 @@
+diff --git a/Makefile b/Makefile
+--- a/Makefile
++++ b/Makefile
+@@ -935,6 +935,9 @@ KBUILD_RUSTFLAGS += -Copt-level=2
+ else ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
+ KBUILD_CFLAGS += -Os
+ KBUILD_RUSTFLAGS += -Copt-level=s
++else ifdef CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3
++KBUILD_CFLAGS += -O3
++KBUILD_RUSTFLAGS += -Copt-level=3
+ endif
+ 
+ # Always set `debug-assertions` and `overflow-checks` because their default
+diff --git a/init/Kconfig b/init/Kconfig
+--- a/init/Kconfig
++++ b/init/Kconfig
+@@ -1622,6 +1622,14 @@ config CC_OPTIMIZE_FOR_SIZE
+ 	  Choosing this option will pass "-Os" to your compiler resulting
+ 	  in a smaller kernel.
+ 
++config CC_OPTIMIZE_FOR_PERFORMANCE_O3
++	bool "Optimize harder for performance (-O3)"
++	help
++	  Build with the "-O3" compiler flag: more inlining, loop
++	  unrolling and vectorization than -O2, at the cost of a larger
++	  kernel image and larger modules. Rust code is built at
++	  opt-level 3.
++
+ endchoice
+ 
+ config HAVE_LD_DEAD_CODE_DATA_ELIMINATION