don't use startup.jl when precompiling, building and testing (#470)

unless the user has explicitly asked for it with
  --startup-file=yes

(cherry picked from commit 40d7f27f2ff08ec466df536f267129a9f5e950b4)
(cherry picked from commit eb96811)

stdlib/Pkg/src/Operations.jl

@@ -1046,7 +1046,7 @@ function build_versions(ctx::Context, uuids::Vector{UUID}; might_need_to_resolve
             """
         cmd = ```
             $(Base.julia_cmd()) -O0 --color=no --history-file=no
-            --startup-file=$(Base.JLOptions().startupfile != 2 ? "yes" : "no")
+            --startup-file=$(Base.JLOptions().startupfile == 1 ? "yes" : "no")
             --compiled-modules=$(Bool(Base.JLOptions().use_compiled_modules) ? "yes" : "no")
             --eval $code
             ```

stdlib/Pkg/src/REPLMode.jl

@@ -1246,7 +1246,6 @@ Create a project called `pkgname` in the current folder.
     precompile
 
 Precompile all the dependencies of the project by running `import` on all of them in a new process.
-The `startup.jl` file is disabled during precompilation unless julia is started with `--startup-file=yes`.
     """,
 ),( CMD_STATUS,
     ["status", "st"],