configure: add pkg-config check for libmysofa

This does require libmysofa with today's latest commit (https://github.com/hoene/libmysofa/commit/08f243d1ec35f6f794aedeb4b187d9f9353bdbc1).
They already had a pkg-config file, but the dependencies weren't setup right. Until now.

configure

@@ -6011,7 +6011,8 @@ enabled libmfx            && { check_pkg_config libmfx libmfx "mfx/mfxvideo.h" M
                                { require libmfx "mfx/mfxvideo.h" MFXInit "-llibmfx $advapi32_extralibs" && warn "using libmfx without pkg-config"; } }
 enabled libmodplug        && require_pkg_config libmodplug libmodplug libmodplug/modplug.h ModPlug_Load
 enabled libmp3lame        && require "libmp3lame >= 3.98.3" lame/lame.h lame_set_VBR_quality -lmp3lame $libm_extralibs
-enabled libmysofa         && require libmysofa "mysofa.h" mysofa_load -lmysofa $zlib_extralibs
+enabled libmysofa         && { check_pkg_config libmysofa libmysofa mysofa.h mysofa_load ||
+                               require libmysofa mysofa.h mysofa_load -lmysofa $zlib_extralibs; }
 enabled libnpp            && { check_lib libnpp npp.h nppGetLibVersion -lnppig -lnppicc -lnppc ||
                                check_lib libnpp npp.h nppGetLibVersion -lnppi -lnppc ||
                                die "ERROR: libnpp not found"; }