Base.runtests: set a temporary Pkg depot path (#42358)

Author: DilumAluthge

base/util.jl

@@ -566,6 +566,7 @@ function runtests(tests = ["all"]; ncores::Int = ceil(Int, Sys.CPU_THREADS::Int
     seed !== nothing && push!(tests, "--seed=0x$(string(seed % UInt128, base=16))") # cast to UInt128 to avoid a minus sign
     ENV2 = copy(ENV)
     ENV2["JULIA_CPU_THREADS"] = "$ncores"
+    ENV2["JULIA_DEPOT_PATH"] = mktempdir(; cleanup = true)
     try
         run(setenv(`$(julia_cmd()) $(joinpath(Sys.BINDIR::String,
             Base.DATAROOTDIR, "julia", "test", "runtests.jl")) $tests`, ENV2))

test/cmdlineargs.jl

@@ -119,7 +119,7 @@ let exename = `$(Base.julia_cmd()) --startup-file=no --color=no`
     # handling of @projectname in --project and JULIA_PROJECT
     let expanded = abspath(Base.load_path_expand("@foo"))
         @test expanded == readchomp(`$exename --project='@foo' -e 'println(Base.active_project())'`)
-        @test expanded == readchomp(setenv(`$exename -e 'println(Base.active_project())'`, "JULIA_PROJECT" => "@foo", "HOME" => homedir()))
+        @test expanded == readchomp(addenv(`$exename -e 'println(Base.active_project())'`, "JULIA_PROJECT" => "@foo", "HOME" => homedir()))
     end
 
     # --quiet, --banner