issue with FFmpeg, not finding pkgconfig package, which I can find with PKG_CONFIG_PATH

kalen@picard:~/src/prefix/extern/FFmpeg$ export PKG_CONFIG_PATH=/home/kalen/src/prefix/install/native/lib/pkgconfig

kalen@picard:~/src/prefix/extern/FFmpeg$ ./configure \
        --disable-everything \
        --disable-doc \
        --pkgconfigdir=/home/kalen/src/prefix/install/native/lib/pkgconfig \
        --arch=x86_64 \
        --enable-gpl \
        --enable-libx264 \
        --enable-encoder=libx264 \
        --enable-decoder=h264 \
        --enable-muxer=mp4 \
        --enable-muxer=matroska \
        --enable-demuxer=mov \
        --enable-demuxer=matroska \
        --enable-parser=h264 \
        --enable-protocol=file \
        --prefix=/home/kalen/src/prefix/install/native \
        --enable-debug \
        --enable-libopus \
        --enable-libfdk-aac \
        --enable-encoder=libopus \
        --enable-encoder=libfdk_aac \
        --enable-decoder=opus \
        --enable-decoder=aac \
        --enable-parser=opus \
        --enable-nonfree
ERROR: opus not found using pkg-config

If you think configure made a mistake, make sure you are using the latest
version from Git.  If the latest version fails, report the problem to the
ffmpeg-user@ffmpeg.org mailing list or IRC #ffmpeg on irc.libera.chat.
Include the log file "ffbuild/config.log" produced by configure as this will help
solve the problem.

kalen@picard:~/src/prefix/extern/FFmpeg$ pkg-config --cflags opus
-I/home/kalen/src/prefix/install/native/include/opus