Add libjxl to pkg_config if enabled

This change was tested using the following command lines:

1) Build/install libaom:
cmake -G Ninja -DCONFIG_TUNE_BUTTERAUGLI=1 -DCMAKE_BUILD_TYPE=Release \
-DENABLE_DOCS=0 -DENABLE_EXAMPLES=0 -DENABLE_TESTDATA=0 \
-DENABLE_TESTS=0 -DENABLE_TOOLS=0 ..
sudo ninja install

2) Build libavif:
cmake -G Ninja .. -DBUILD_SHARED_LIBS=OFF -DAVIF_CODEC_AOM=ON \
-DAVIF_LOCAL_AOM=OFF -DAVIF_BUILD_EXAMPLES=ON -DAVIF_BUILD_APPS=ON \
-DAVIF_BUILD_TESTS=ON -DCMAKE_BUILD_TYPE=Release
ninja

3) Run avifenc with tune=butteraugli:
./avifenc -y 420 --min 0 --max 63 -s 6 -j 4 -a end-usage=q \
-a cq-level=18 -a tune=butteraugli ${input} ${output}

Change-Id: I01ff17cd57de06dfa04d11e91d12d2ce64e89a2c
diff --git a/build/cmake/aom_install.cmake b/build/cmake/aom_install.cmake
index bcc0ab5..2c0e7a5 100644
--- a/build/cmake/aom_install.cmake
+++ b/build/cmake/aom_install.cmake
@@ -47,6 +47,7 @@
               -DCMAKE_PROJECT_NAME=${CMAKE_PROJECT_NAME}
               -DCONFIG_MULTITHREAD=${CONFIG_MULTITHREAD}
               -DCONFIG_TUNE_VMAF=${CONFIG_TUNE_VMAF}
+              -DCONFIG_TUNE_BUTTERAUGLI=${CONFIG_TUNE_BUTTERAUGLI}
               -DHAVE_PTHREAD_H=${HAVE_PTHREAD_H}
               -P
               "${AOM_ROOT}/build/cmake/pkg_config.cmake"
diff --git a/build/cmake/pkg_config.cmake b/build/cmake/pkg_config.cmake
index 4466cbb..e8fff2e 100644
--- a/build/cmake/pkg_config.cmake
+++ b/build/cmake/pkg_config.cmake
@@ -55,6 +55,9 @@
 if(CONFIG_TUNE_VMAF)
   file(APPEND "${pkgconfig_file}" " libvmaf")
 endif()
+if(CONFIG_TUNE_BUTTERAUGLI)
+  file(APPEND "${pkgconfig_file}" " libjxl")
+endif()
 file(APPEND "${pkgconfig_file}" "\nConflicts:\n")
 file(APPEND "${pkgconfig_file}" "Libs: -L\${libdir} -l${pkg_name}\n")
 if(CONFIG_MULTITHREAD AND HAVE_PTHREAD_H)