Fix up "sage -p"

[mkoeppe]

$ ./sage -p sagetex
Found local metadata for sagetex-3.5
Using cached file /Users/mkoeppe/s/sage/sage-rebasing/upstream/sagetex-3.5.tar.gz
mkdir: : No such file or directory
************************************************************************
Error creating directory 
************************************************************************

[mkoeppe]

Branch is on top of #29500 because it touches the same code

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Last 10 new commits:

​0a64674	build/pkgs/gambit/spkg-install.in: Install via bdist_wheel
​ca58693	build/pkgs/pillow/spkg-install.in: Install via bdist_wheel
​5a747c4	build/bin/sage-pip-{install,uninstall}: Remove pip2 support
​9ee2110	build/bin/sage-dist-helpers: Also use $sudo for storing the wheel file
​d7aac84	src/doc/en/developer/packaging.rst: Update sdh_... documentation
​9b7c7a0	build/bin/sage-pip-{install,uninstall}: Fix typo in comment
​4135e8b	build/bin/sage-pip-install: Remove an outdated comment
​f2e7075	Merge tag '9.2.beta13' into t/29500/install_all_python_packages_via_pip_wheel__create_pep_503_simple_repository_for_wheels
​bd0fd2f	Merge branch 't/29500/install_all_python_packages_via_pip_wheel__create_pep_503_simple_repository_for_wheels' into t/30657/fix_up__sage__p_
​2e20f23	build/bin/sage-spkg: Move SAGE_SPKG_{INST,SCRIPTS,WHEELS} setting here from build/bin/install, make them relative to SAGE_INST_LOCAL

[mjo]

Looks OK I guess. The build/bin/sage-spkg script obviously needs these variables set, so it makes sense to move them "up" out of build/make/install where they are not used directly.

[mkoeppe]

Thanks.

[vbraun]

Fails while building sage_conf-none for me... do incremental builds work?

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​be2417c	Merge tag '9.2.beta14' into t/30657/fix_up__sage__p_
​8ee7ee2	build/make/install: Set SAGE_SPKG_WHEELS also here so that script packages still work

[mjo]

The new commit is reverted on the #29386 branch, but looks good for now.

[mkoeppe]

Thanks!