Several install_deps issues

Please fix these install_deps.sh issues:

(1)
The command line for building blender that install_deps is creating contains the wrong python version 3.7 (here on manjaro 3.8 is standard):

-D PYTHON_VERSION=3.7

Every time I run install_deps, I have to correct this manually. Can it be fixed?

(2)
It seems as if OpenXR and Alembic are downloaded, unpacked and compiled every time install_deps.sh is run (just today it happened five times in a row)

Building Alembic-1.7.12

Connecting to github.com (github.com)|140.82.118.4|:443… connected.

Unpacking Alembic-1.7.12

make -f CMakeFiles/Makefile2 all

(3)
running install_deps without any parameter regarding USD, e.g.

install_deps.sh --with-all --with-oidn --skip-osl

results in


Own USD-19.11 is up to date, nothing to do!
If you want to force rebuild of this lib, use the --force-usd option.

Running ldconfig for usd…

If you’re using CMake add this to your configuration flags:

-D WITH_USD=ON

Or even simpler, just run (in your blender-source dir):
make -j16 BUILD_CMAKE_ARGS="-U SNDFILE -U PYTHON -U BOOST -U Boost -U OPENCOLORIO -U OPENEXR -U OPENIMAGEIO -U LLVM -U CYCLES -U OPENSUBDIV -U OPENVDB -U COLLADA -U FFMPEG -U ALEMBIC -U USD -D WITH_CODEC_SNDFILE=ON -D PYTHON_VERSION=3.7 -D WITH_OPENCOLORIO=ON -D WITH_CYCLES_OSL=OFF -D WITH_LLVM=OFF -D WITH_OPENSUBDIV=ON -D WITH_OPENVDB=ON -D WITH_OPENVDB_BLOSC=ON -D WITH_OPENCOLLADA=ON -D WITH_CYCLES_EMBREE=ON -D WITH_OPENIMAGEDENOISE=ON -D OPENIMAGEDENOISE_ROOT_DIR=/home/mick/blender-git/deps/oidn -D WITH_JACK=ON -D WITH_JACK_DYNLOAD=ON -D WITH_ALEMBIC=ON -D ALEMBIC_ROOT_DIR=/home/mick/blender-git/deps/alembic -D WITH_USD=ON -D WITH_CODEC_FFMPEG=ON -D FFMPEG_LIBRARIES=‘avformat;avcodec;avutil;avdevice;swscale;swresample;lzma;rt;theora;theoradec;theoraenc;vorbis;vorbisenc;vorbisfile;ogg;xvidcore;vpx;opus;mp3lame;x264;openjp2’ -D WITH_XR_OPENXR=ON -D XR_OPENXR_SDK_ROOT_DIR=/home/mick/blender-git/deps/xr-openxr-sdk"

But when building blender with this command, it will not include USD (even with --with-usd it is not included successfully):

...
-- Could NOT find USD (missing: USD_LIBRARY USD_INCLUDE_DIR) 
...
- WITH_USD                    OFF