fix compiler errors and warnings

Problems that were fixed:
  - gcc crate deprecated compile_library
  - `cargo test -p kvm` had a compile error
  - `cargo test -p kvm_sys` failed to link with libc
  - main.rs failed to include `getpid` and had dead code
  - fork.rs had a warning in `cargo test -p sys_util`
  - unused const in serial.rs

BUG=None
TEST=sudo cargo test -p data_model -p io_jail -p kernel_loader -p kvm \
     -p kvm_sys -p net_sys -p net_util -p syscall_defines -p sys_util \
     -p virtio_sys -p vhost -p x86_64 -p crosvm

Change-Id: Iaf0389013fbcdfbfaa7cf37ea1a1fc045f480ada
Reviewed-on: https://chromium-review.googlesource.com/642509
Commit-Ready: Zach Reizner <zachr@chromium.org>
Tested-by: Zach Reizner <zachr@chromium.org>
Reviewed-by: Jason Clinton <jclinton@chromium.org>
Reviewed-by: Stephen Barber <smbarber@chromium.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/kvm/src/lib.rs b/kvm/src/lib.rs
index 4f2d3a6..f2a45db 100644
--- a/kvm/src/lib.rs
+++ b/kvm/src/lib.rs
@@ -759,7 +759,7 @@ mod tests {
         let kvm = Kvm::new().unwrap();
         let gm = GuestMemory::new(&vec![(GuestAddress(0), 0x1000)]).unwrap();
         let mut vm = Vm::new(&kvm, gm).unwrap();
-        assert!(vm.remove_device_memory(0).unwrap());
+        assert!(vm.remove_device_memory(0).is_err());
     }
 
      #[test]