riscv: Use -O2 by default for riscv

gcc 14.3 has bus compiling with -Os on riscv, use -O2 by default. Is there
some way to prevent applications from selecting -Os?

Signed-off-by: Keith Packard <[email protected]>

Author: keith-packard

cmake/zephyr/Kconfig

@@ -23,6 +23,9 @@ config PICOLIBC_DEFAULT
 	help
 	  Zephyr SDK >=0.17.1 always uses Picolibc
 
+# libstdc++ is built without exception support in -Os mode
+# gcc 14.3 has bugs compiling with -Os on riscv
 choice COMPILER_OPTIMIZATIONS
 	default SPEED_OPTIMIZATIONS if ("$(TOOLCHAIN_VARIANT_COMPILER)" = "gnu") && CPP_EXCEPTIONS
+	default SPEED_OPTIMIZATIONS if ("$(TOOLCHAIN_VARIANT_COMPILER)" = "gnu") && RISCV
 endchoice