我通过输入gcc -march命令获得gcc --target-help的帮助：
-march=CPU[,+EXTENSION...]
generate code for CPU and EXTENSION, CPU is one of: i8086,
i186, i286, i386, i486, pentium, pentiumpro, pentiumii,
pentiumiii, pentium4, prescott, nocona, core, core2,
corei7, l1om, k6, k6_2, athlon, k8, amdfam10, generic32,
generic64 EXTENSION is combination of: 8087, 287, 387,
no87, mmx, nommx, sse, sse2, sse3, ssse3, sse4.1, sse4.2,
sse4, nosse, avx, noavx, vmx, smx, xsave, movbe, ept, aes,
pclmul, fma, clflush, syscall, rdtscp, 3dnow, 3dnowa,
sse4a, svme, abm, padlock, fma4, xop, lwp
我尝试设置-march=i686+nommx和-march=i686,+nommx，但这不正确！ gcc报告错误：error: bad value (i686,+nommx) for -march= switch
我想将我的程序构建到i686而没有mmx目标，如何设置-march选项？