Merge remote-tracking branch 'remotes/bonzini-gitlab/tags/for-upstream' into staging

meson fixes:
* fix PIE default for Windows
* tweak conditions for requiring SDL2 and pixman
* move NSIS building to Meson
* fix creation of systemtap files
* add --ninja option for Windows builds
* other fixes for stupid bugs and for Windows paths

meson related:
* forward port of dtrace fix for MacOS
* change colorout option to auto

# gpg: Signature made Thu 27 Aug 2020 17:58:21 BST
# gpg:                using RSA key F13338574B662389866C7682BFFBD25F78C7AE83
# gpg:                issuer "[email protected]"
# gpg: Good signature from "Paolo Bonzini <[email protected]>" [full]
# gpg:                 aka "Paolo Bonzini <[email protected]>" [full]
# Primary key fingerprint: 46F5 9FBD 57D6 12E7 BFD4  E2F7 7E15 100C CD36 69B1
#      Subkey fingerprint: F133 3857 4B66 2389 866C  7682 BFFB D25F 78C7 AE83

* remotes/bonzini-gitlab/tags/for-upstream:
  ninjatool: Fixes E$$: in generated Makefile.ninja
  meson: set colorout to auto
  meson: Mingw64 gcc doesn't recognize system include_type for sdl2
  meson: fix relpath failure on Win32
  ninjatool: quote dollars in variables
  meson: don't require CONFIG_VTE for the GTK UI
  meson: cleanup xkbcommon detection
  configure: add --ninja option
  meson: skip SDL2 detection if --disable-system
  meson: move pixman detection to meson
  configure: default to PIE disabled on Windows platforms
  meson: Fix chardev-baum.so name
  meson: Fix meson build with --enable-libdaxctl
  scripts/qemu-version.sh: Add missing space before ']'
  meson: Don't make object files for dtrace on macOS
  meson: Build qemu-nbd on macOS again
  trace: fix creation of systemtap files

Signed-off-by: Peter Maydell <[email protected]>