Fails to build on x86 without SSE

[jbeich]

i386 target on FreeBSD, NetBSD, OpenBSD (and maybe some Linux distributions) lacks SSE unless -msse is passed. For one, FreeBSD i386 targets -march=i486 by default but may switch to -march=i586 soon.

$ c++ -v
FreeBSD clang version 8.0.0 (tags/RELEASE_800/final 356365) (based on LLVM 8.0.0)
Target: i386-unknown-freebsd11.3
Thread model: posix
InstalledDir: /usr/bin

$ meson _build
$ ninja -C _build
[...]
FAILED: vmaf@sta/src_libvmaf_src_adm_tools.c.o
cc -Ivmaf@sta -I. -I.. -I.././src/ptools/opencontainers_1_8_4/include -I.././src/libvmaf/src/ -I.././src/libvmaf/src/common -I.././src/ptools/ -Xclang -fcolor-diagnostics -pipe -Wall -Winvalid-pch -g -fPIC -std=c99 -w -Wextra -pedantic -D_FILE_OFFSET_BITS=64 '-D MULTI_THREADING' -DOC_NEW_STYLE_INCLUDES -MD -MQ 'vmaf@sta/src_libvmaf_src_adm_tools.c.o' -MF 'vmaf@sta/src_libvmaf_src_adm_tools.c.o.d' -o 'vmaf@sta/src_libvmaf_src_adm_tools.c.o' -c ../src/libvmaf/src/adm_tools.c
../src/libvmaf/src/adm_tools.c:36:16: error: always_inline function '_mm_cvtss_f32' requires target feature 'sse', but would be inlined into function 'rcp_s' that is compiled without support for 'sse'
    float xi = _mm_cvtss_f32(_mm_rcp_ss(_mm_load_ss(&x)));
               ^
../src/libvmaf/src/adm_tools.c:36:30: error: always_inline function '_mm_rcp_ss' requires target feature 'sse', but would be inlined into function 'rcp_s' that is compiled without support for 'sse'
    float xi = _mm_cvtss_f32(_mm_rcp_ss(_mm_load_ss(&x)));
                             ^
../src/libvmaf/src/adm_tools.c:36:41: error: always_inline function '_mm_load_ss' requires target feature 'sse', but would be inlined into function 'rcp_s' that is compiled without support for 'sse'
    float xi = _mm_cvtss_f32(_mm_rcp_ss(_mm_load_ss(&x)));
                                        ^
3 errors generated.