title: Go 1.5+ : Error - imports runtime: C source files not allowed when not using cgo or SWIG
body: <p>My program was building perfectly with go 1.4.2. After installing go 1.5, I am getting following error.</p>
  
  <blockquote>
    <p>imports runtime: C source files not allowed when not using cgo or
    SWIG: atomic_amd64x.c defs.c float.c heapdump.c lfstack.c malloc.c
    mcache.c mcentral.c mem_linux.c mfixalloc.c mgc0.c mheap.c msize.c
    os_linux.c panic.c parfor.c proc.c runtime.c signal.c signal_amd64x.c
    signal_unix.c stack.c string.c sys_x86.c vdso_linux_amd64.c</p>
  </blockquote>
  
  <p>The error is not program dependent. Even a "Hello world" programs is throwing the same error.</p>