arch/sparc64: remove -mv8plus

This is used to force the global registers and out registers to be
64-bit wide, for Solaris 32-bit mode only.

Author: Cyanoxygen

arch/sparc64.sh

@@ -6,6 +6,6 @@
 CFLAGS_COMMON_ARCH=('-O2' '-fno-tree-ch' '-ffunction-sections' '-fdata-sections')
 LDFLAGS_COMMON_ARCH=('-Wl,--gc-sections')
 
-CFLAGS_COMMON_ARCH+=('-march=v9' '-mv8plus' '-mvis' '-m64' '-mcmodel=medany')
+CFLAGS_COMMON_ARCH+=('-march=v9' '-mvis' '-m64' '-mcmodel=medany')
 
 RUSTFLAGS_COMMON_ARCH=('-Ctarget-cpu=v9' '-Ctarget-feature=+vis' '-Ccode-model=medium')