Description of problem:
rpmdev-setuptree overrides %_smp_mflags macro by writing one of its own into users ~/.rpmmacros. This causes any improvements done to the central version of this macro go down the toilet because the one in ~/.rpmmacros is never updated once written. For example it does not honor %_smp_ncpus_max macro which caused me a fair amount of unnecessary head-scratching to figure where the -j3 was coming from in a copr build, despite setting %_smp_ncpus_max to 1 in spec.

Please stop overriding the macro. 

Version-Release number of selected component (if applicable):
rpmdevtools-8.5-1, git head apparently as well

How reproducible:
Always

Steps to Reproduce:

[luser@localhost ~]$ rpm --eval "%{_smp_mflags}"
-j4
[luser@localhost ~]$ rpm --define "%_smp_ncpus_max 1" --eval "%{_smp_mflags}"

[luser@localhost ~]$ rpmdev-setuptree 
[luser@localhost ~]$ rpm --eval "%{_smp_mflags}"
-j4
[luser@localhost ~]$ rpm --define "%_smp_ncpus_max 1" --eval "%{_smp_mflags}"
-j4

Note that this is NOT a request for adding %_smp_ncpus_max support, but to stop overriding what could be considered a system macro for no really good reason. The original point was to force parallel build on non-smp systems to shake out makefile bugs. Most systems are smp these days so the original point is largely lost by now, but it has negative effect on other users.