bug#51213: ghci missing reference to gcc

[Jack Hill]

Hi Guix,

Using Guix 5fafb6e792c1e18ec223f0c7fb350d0c9b962a45, running ghci in an 
environment can't find gcc:

$ guix environment --ad-hoc ghc -- ghci
GHCi, version 8.10.7: https://www.haskell.org/ghc/  :? for help
ghc: could not execute: gcc

but if gcc-toolchain is included, it can:

$ guix environment --ad-hoc ghc gcc-toolchain -- ghci
substitute: updating substitutes from 'https://ci.guix.gnu.org'... 100.0%
substitute: updating substitutes from 'https://bordeaux.guix.gnu.org'... 
100.0%
The following derivation will be built:
   /gnu/store/dqga43d50f6n1isazmi4cx83l3hyhsz5-profile.drv

60.0 MB will be downloaded
substitute: updating substitutes from 'https://ci.guix.gnu.org'... 100.0%
 gcc-11.2.0-lib  5.0MiB 
1.5MiB/s 00:03 [##################] 100.0%
 gcc-11.2.0  30.7MiB 
2.4MiB/s 00:13 [##################] 100.0%
 gcc-toolchain-11.2.0  5KiB 
40KiB/s 00:00 [##################] 100.0%
building CA certificate bundle...
listing Emacs sub-directories...
building fonts directory...
building GHC package cache...
building directory of Info manuals...
building database for manual pages...
building profile with 2 packages...
GHCi, version 8.10.7: https://www.haskell.org/ghc/  :? for help
Prelude>

Best,
Jack