Shake out some assumptions about architecture of host platform

src/BuildToolchains.jl

@@ -125,12 +125,16 @@ meson_cxx_link_args(p::AbstractPlatform) = meson_c_link_args(p)
 meson_objc_link_args(p::AbstractPlatform) = meson_c_link_args(p)
 meson_fortran_link_args(p::AbstractPlatform) = meson_c_link_args(p)
 
-# We can run native programs only on
+# We can run native programs only if the platform matches the default host
+# platform, but when this is `x86_64-linux-musl` we can run executables for
 # * i686-linux-gnu
 # * x86_64-linux-gnu
 # * x86_64-linux-musl
 function meson_is_foreign(p::AbstractPlatform)
-    if Sys.islinux(p) && proc_family(p) == "intel" && (libc(p) == "glibc" || (libc(p) == "musl" && arch(p) == "x86_64"))
+    if platforms_match(p, default_host_platform) ||
+        (platforms_match(default_host_platform, Platform("x86_64", "linux"; libc="musl"))
+         && Sys.islinux(p) && proc_family(p) == "intel" &&
+             (libc(p) == "glibc" || (libc(p) == "musl" && arch(p) == "x86_64")))
         # Better to explicitly return the string we expect rather than
         # relying on the representation of the boolean values (even though
         # the result is the same)

src/Platforms.jl

@@ -14,7 +14,7 @@ Base.BinaryPlatforms.tags(p::AnyPlatform) = Dict{String,String}()
 Base.BinaryPlatforms.triplet(::AnyPlatform) = "any"
 Base.BinaryPlatforms.arch(::AnyPlatform) = "any"
 Base.BinaryPlatforms.os(::AnyPlatform) = "any"
-nbits(::AnyPlatform) = 64
+nbits(::AnyPlatform) = nbits(default_host_platform)
 proc_family(::AnyPlatform) = "any"
 Base.show(io::IO, ::AnyPlatform) = print(io, "AnyPlatform")
 

src/Rootfs.jl

@@ -631,7 +631,7 @@ function choose_shards(p::AbstractPlatform;
     return shards
 end
 
-# XXX: we want AnyPlatform to look like `x86_64-linux-musl` in the build environment.
+# We want AnyPlatform to look like `default_host_platform` in the build environment.
 choose_shards(::AnyPlatform; kwargs...) = choose_shards(default_host_platform; kwargs...)
 
 """

src/Runner.jl

@@ -11,7 +11,7 @@ export default_host_platform
 
 The default host platform in the build environment.
 """
-const default_host_platform = Platform("x86_64", "linux"; libc="musl", cxxstring_abi="cxx11")
+const default_host_platform = Platform(arch(HostPlatform()), "linux"; libc="musl", cxxstring_abi="cxx11")
 
 function nbits(p::AbstractPlatform)
     if arch(p) in ("i686", "armv6l", "armv7l")
@@ -44,7 +44,7 @@ function aatriplet(p::AbstractPlatform)
     t = replace(t, "armv6l" => "arm")
     return t
 end
-# XXX: we want AnyPlatform to look like `x86_64-linux-musl` in the build environment.
+# We want AnyPlatform to look like `default_host_platform` in the build environment.
 aatriplet(p::AnyPlatform) = aatriplet(default_host_platform)
 
 function ld_library_path(target::AbstractPlatform,
@@ -896,7 +896,7 @@ function platform_envs(platform::AbstractPlatform, src_name::AbstractString;
         "dlext" => platform_dlext(platform),
         "exeext" => platform_exeext(platform),
         "PATH" => "/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin",
-        "MACHTYPE" => "x86_64-linux-musl",
+        "MACHTYPE" => aatriplet(default_host_platform),
 
         # Set location parameters
         "WORKSPACE" => "/workspace",

src/utils.jl

@@ -57,6 +57,6 @@ function get_concrete_platform(platform::AbstractPlatform; kwargs...)
     return get_concrete_platform(platform, shards)
 end
 
-# XXX: we want the AnyPlatform to look like `x86_64-linux-musl`,
+# We want the AnyPlatform to look like `default_host_platform`,
 get_concrete_platform(::AnyPlatform, shards::Vector{CompilerShard}) =
     get_concrete_platform(default_host_platform, shards)

test/platforms.jl

@@ -39,7 +39,7 @@ end
     @test arch(AnyPlatform()) == "any"
     @test repr(AnyPlatform()) == "AnyPlatform"
 
-    # In the build environment we want AnyPlatform to look like x86_64-linux-musl
+    # In the build environment we want AnyPlatform to look like `default_host_platform`
     @test get_concrete_platform(
             AnyPlatform();
             compilers = [:c],

test/runners.jl

@@ -73,14 +73,14 @@ end
         @info("Beginning full shard test... (this can take a while)")
         platforms = supported_platforms()
     else
-        platforms = (Platform("x86_64", "linux"; libc="musl"),)
+        platforms = (default_host_platform,)
     end
 
     # Checks that the wrappers provide the correct C++ string ABI
     @testset "Compilation - C++ string ABI" begin
         mktempdir() do dir
             # Host is x86_64-linux-musl-cxx11 and target is x86_64-linux-musl-cxx03
-            ur = preferred_runner()(dir; platform=Platform("x86_64", "linux"; libc="musl", cxxstring_abi="cxx03"), preferred_gcc_version=v"5")
+            ur = preferred_runner()(dir; platform=Platform(arch(HostPlatform()), "linux"; libc="musl", cxxstring_abi="cxx03"), preferred_gcc_version=v"5")
             iobuff = IOBuffer()
             test_script = raw"""
             set -e