Consistently use Base.julia_cmd() in tests (#706)

This ensures we use same flags as parent Julia process and avoid invalidating the cache, which would then lead to multiple julia processes recompiling the cache at the same time and causing race conditions.

Author: giordano

test/mpiexecjl.jl

@@ -7,13 +7,17 @@ using MPI
         # `mpiexecjl`
         Pkg.activate(dir; io=devnull)
         Pkg.develop(PackageSpec(path=joinpath(@__DIR__, "..")); io=devnull)
+        # Precompile in advance to avoid race conditions when running multiple Julia
+        # processes in parallel.
+        Pkg.precompile(; io=devnull)
         # Test installation
         @test_logs (:info, r"Installing") (:info, r"Done") MPI.install_mpiexecjl(; destdir = dir)
         # Test a run of mpiexec
         nprocs_str = get(ENV, "JULIA_MPI_TEST_NPROCS", "")
         nprocs = nprocs_str == "" ? clamp(Sys.CPU_THREADS, 2, 4) : parse(Int, nprocs_str)
         mpiexecjl = joinpath(dir, "mpiexecjl")
-        julia = joinpath(Sys.BINDIR, Base.julia_exename())
+        # `Base.julia_cmd()` ensures keeping consistent flags when running subprocesses.
+        julia = Base.julia_cmd()
         example = joinpath(@__DIR__, "..", "docs", "examples", "01-hello.jl")
         env = ["JULIA_BINDIR" => Sys.BINDIR]
         p = withenv(env...) do

test/test_spawn.jl

@@ -8,7 +8,8 @@ const N = clamp(Sys.CPU_THREADS, 2, 4)
 exename = joinpath(Sys.BINDIR, Base.julia_exename())
 @test isfile(exename)
 errors = Vector{Cint}(undef, N-1)
-intercomm = MPI.Comm_spawn(exename, [joinpath(@__DIR__, "spawned_worker.jl")], N-1, MPI.COMM_WORLD, errors)
+# Ensure using consistent flags when spawning subprocesses by using same arguments as `Base.julia_cmd`.
+intercomm = MPI.Comm_spawn(exename, vcat(Base.julia_cmd()[2:end], joinpath(@__DIR__, "spawned_worker.jl")), N-1, MPI.COMM_WORLD, errors)
 @test errors == zeros(Cint,N-1)
 world_comm = MPI.Intercomm_merge(intercomm, false)