Failure on Windows

[musm]

It looks like the script doesn't automatically find the system compiler on Windows or use WinRPM. This https://github.com/JuliaLang/julia/blob/master/contrib/build_sysimg.jl#L110 function would be helpful.

$ julia juliac.jl test.jl
Program file:
C:\Users\Mus\static-julia\test.jl
Change directory:
"C:\Users\Mus\static-julia\builddir"
Running command:
`'C:\Julia\Julia-0.6-latest\bin\julia.exe' -Cx86-64 '-JC:\Julia\Julia-0.6-latest\lib\julia\sys.dll' --compile=yes --depwarn=yes --startup-file=no --output-o test.o -e 'include("C:\\Users\\Mus\\static-julia\\test.jl"); push!(Base.LOAD_CACHE_PATH, "C:\\Users\\Mus\\.julia\\lib\\v0.6"); empty!(Base.LOAD_CACHE_PATH)'`
"HELLO" = "HELLO"
Running command:
`gcc -m64 -shared -o libtest.dll test.o -std=gnu99 '-IC:\Julia\Julia-0.6-latest\include\julia' -DJULIA_ENABLE_THREADING=1 '-LC:\Julia\Julia-0.6-latest\bin' -Wl,--stack,8388608 -ljulia -lopenlibm '-Wl,-rpath,$ORIGIN' -Wl,--export-all-symbols`
ERROR: LoadError: could not spawn `gcc -m64 -shared -o libtest.dll test.o -std=gnu99 '-IC:\Julia\Julia-0.6-latest\include\julia' -DJULIA_ENABLE_THREADING=1 '-LC:\Julia\Julia-0.6-latest\bin' -Wl,--stack,8388608 -ljulia -lopenlibm '-Wl,-rpath,$ORIGIN' -Wl,--export-all-symbols`: no such file or directory (ENOENT)
Stacktrace:
 [1] _jl_spawn(::String, ::Array{String,1}, ::Ptr{Void}, ::Base.Process, ::RawFD, ::RawFD, ::RawFD) at .\process.jl:360
 [2] #375 at .\process.jl:512 [inlined]
 [3] setup_stdio(::Base.##375#376{Cmd}, ::Tuple{RawFD,RawFD,RawFD}) at .\process.jl:499
 [4] #spawn#374(::Nullable{Base.ProcessChain}, ::Function, ::Cmd, ::Tuple{RawFD,RawFD,RawFD}) at .\process.jl:511
 [5] run(::Cmd) at .\process.jl:650
 [6] julia_compile(::String) at C:\Users\Mus\static-julia\juliac.jl:49
 [7] main() at C:\Users\Mus\static-julia\juliac.jl:64
 [8] include_from_node1(::String) at .\loading.jl:569
 [9] include(::String) at .\sysimg.jl:14
 [10] process_options(::Base.JLOptions) at .\client.jl:305
 [11] _start() at .\client.jl:371
while loading C:\Users\Mus\static-julia\juliac.jl, in expression starting on line 67