perf: opt-out of lto usage

perf: opt-out of lto usage

This fixes building with USE_LTO enabled:

mold: error: undefined symbol: __memset
>>> referenced by <artificial>
>>>               ./tmp/ccsgR7G6.ltrans10.ltrans.o
mold: error: undefined symbol: memset_orig
>>> referenced by <artificial>
>>>               ./tmp/ccsgR7G6.ltrans10.ltrans.o
mold: error: undefined symbol: perf_regs_load
>>> referenced by <artificial>
>>>               ./tmp/ccsgR7G6.ltrans15.ltrans.o:(test_dwarf_unwind__thread)
mold: error: undefined symbol: memset_erms
>>> referenced by <artificial>
>>>               ./tmp/ccsgR7G6.ltrans10.ltrans.o
mold: error: undefined symbol: memcpy_orig
>>> referenced by <artificial>
>>>               ./tmp/ccsgR7G6.ltrans10.ltrans.o
mold: error: undefined symbol: memcpy_erms
>>> referenced by <artificial>
>>>               ./tmp/ccsgR7G6.ltrans10.ltrans.o
mold: error: undefined symbol: __memcpy
>>> referenced by <artificial>
>>>               ./tmp/ccsgR7G6.ltrans10.ltrans.o
collect2: error: ld returned 1 exit status
make[5]: *** [Makefile.perf:670: ../openwrt/linux/tools/perf-target-x86_64_musl/perf] Error 1
make[4]: *** [Makefile.perf:238: sub-make] Error 2
make[3]: *** [Makefile:70: all] Error 2
make[2]: *** [Makefile:84: ./build_dir/target-x86_64_musl/linux-x86_64/linux-5.15.120/tools/perf-target-x86_64_musl/.built] Error 2
make[2]: Leaving directory './package/devel/perf'
time: package/devel/perf/compile#55.88#6.78#12.89
    ERROR: package/devel/perf failed to build.

Signed-off-by: Javier Marcet <javier@marcet.info>