precompilepkgs: simplify custom config printing if only one (#53805)

Currently it's a bit excessive in the `Pkg.test` precompile job

![Screenshot 2024-03-20 at 12 04
03 PM](https://github.com/JuliaLang/julia/assets/1694067/7600f0b8-6e4b-43b2-9c42-c8d5d16b8d57)


This PR
```
Precompiling project for configuration --code-coverage=none --color=yes --check-bounds=yes --warn-overwrite=yes --depwarn=yes --inline=yes --startup-file=no --track-allocation=none...
    354.9 ms  ✓ RFFT
  1 dependency successfully precompiled in 1 seconds. 38 already precompiled.
```

Pkg could also just set the non-default flags to minimize the list.

base/precompilation.jl

@@ -551,11 +551,14 @@ function precompilepkgs(pkgs::Vector{String}=String[];
  else
  target = "project"
  end
- nconfig = length(configs)
- if nconfig > 1
- target *= " for $nconfig compilation configurations..."
- else
+ nconfigs = length(configs)
+ if nconfigs == 1
+ if !isempty(only(configs)[1])
+ target *= " for configuration $(join(only(configs)[1], " "))"
+ end
  target *= "..."
+ else
+ target *= " for $nconfigs compilation configurations..."
  end
  @debug "precompile: packages filtered"
 
@@ -677,7 +680,7 @@ function precompilepkgs(pkgs::Vector{String}=String[];
  loaded = warn_loaded && haskey(Base.loaded_modules, dep)
  _name = haskey(exts, dep) ? string(exts[dep], " → ", dep.name) : dep.name
  name = dep in direct_deps ? _name : string(color_string(_name, :light_black))
- if !isempty(config[1])
+ if nconfigs > 1 && !isempty(config[1])
  config_str = "$(join(config[1], " "))"
  name *= color_string(" $(config_str)", :light_black)
  end
@@ -769,7 +772,7 @@ function precompilepkgs(pkgs::Vector{String}=String[];
 
  _name = haskey(exts, pkg) ? string(exts[pkg], " → ", pkg.name) : pkg.name
  name = is_direct_dep ? _name : string(color_string(_name, :light_black))
- if !isempty(flags)
+ if nconfigs > 1 && !isempty(flags)
  config_str = "$(join(flags, " "))"
  name *= color_string(" $(config_str)", :light_black)
  end