chore(rom/deb): Fix wrong install directory for rpm/deb

[zemzale]

Description
Since glab is built into a 'bin' directory it just ends up installing
into '/usr/local/bin/bin' instead of '/usr/local/bin/'.

Related Issue

Resolves #508

How Has This Been Tested?

 docker run --rm -v $PWD/dist:/rt debian:latest dpkg -c /rt/glab_v1.12.1_Linux_x86_64.deb
 drwxr-xr-x 0/0               0 2021-01-05 08:06 ./usr/
 drwxr-xr-x 0/0               0 2021-01-05 08:06 ./usr/local/
 drwxr-xr-x 0/0               0 2021-01-05 08:06 ./usr/local/bin/
 -rwxr-xr-x 0/0        17436672 2021-01-05 08:06 ./usr/local/bin/glab

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation
• Chore (Related to CI or Packaging to platforms)

[codecov]

Codecov Report

Merging #512 (4b47d9c) into trunk (a3fda2e) will increase coverage by 11.80%.
The diff coverage is 61.60%.

@@             Coverage Diff             @@
##            trunk     #512       +/-   ##
===========================================
+ Coverage   46.62%   58.43%   +11.80%     
===========================================
  Files         116       85       -31     
  Lines        6224     5726      -498     
===========================================
+ Hits         2902     3346      +444     
+ Misses       2998     2034      -964     
- Partials      324      346       +22     

Impacted Files	Coverage Δ
commands/alias/expand/alias_expand.go	39.21% <0.00%> (ø)
commands/auth/login/login.go	46.45% <0.00%> (+8.38%)	⬆️
commands/cmdutils/cmdutils.go	46.90% <0.00%> (ø)
commands/cmdutils/factory.go	0.00% <0.00%> (-69.24%)	⬇️
commands/config/config.go	37.93% <0.00%> (-23.81%)	⬇️
commands/issue/board/create/issue_board_create.go	74.19% <0.00%> (-5.12%)	⬇️
commands/project/archive/repo_archive.go	0.00% <0.00%> (-26.03%)	⬇️
commands/project/create/project_create.go	0.00% <0.00%> (-11.28%)	⬇️
internal/config/config.go	0.00% <0.00%> (ø)
internal/git/git.go	32.05% <0.00%> (-17.08%)	⬇️
... and 101 more

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[profclems]

Thanks for taking this on!