program-locations is undocumented

[lf-]

Describe the bug

I cannot find any documentation on the cabal.project reference about the program-locations stanza.

Sample usage:

  program-locations
    gcc-location: /usr/bin/clang

To Reproduce

co/cabal - [master] » rg program-locations
cabal-install/src/Distribution/Client/ProjectConfig.hs
1446: ++ "specify the path in a global 'program-locations' section."

cabal-install/src/Distribution/Client/ProjectConfig/Legacy.hs
1384:      sectionName        = "program-locations",
1392:            syntaxError lineno "the section 'program-locations' takes no arguments"

cabal-install/src/Distribution/Client/Sandbox/PackageEnvironment.hs
220:    isKnownSection (ParseUtils.Section _ "program-locations" _ _)       = True
246:                  (ParseUtils.Section _ "program-locations" name fs)
250:          warning "The 'program-locations' section should be unnamed"

cabal-install/src/Distribution/Client/Config.hs
1153:    isKnownSection (ParseUtils.Section _ "program-locations" _ _)       = True
1232:                 (ParseUtils.Section _ "program-locations" name fs)
1236:          warning "The 'program-locations' section should be unnamed"
1304:  $+$ configFlagsSection "program-locations" withProgramsFields
1391:-- | Fields for the 'program-locations' section.