pixman: bump to version 0.38.4

pixman: bump to version 0.38.4

This version bump contains mainly fixes for the build system

  e8df10e Pre-release version bump to 0.38.4
  23f036d Makefile.am: Ship Meson assembly test files in the tarball
  e7058fe Makefile.am: Update download links
  8888e75 Post-release version bump to 0.38.3
  a7ffb3e Pre-release version bump to 0.38.2
  4c4753c meson: Correct copy-and-paste mistake
  7295983 void function should not return a value
  ef4fb03 Windows: Support building with SHELL=cmd.exe
  55d8f95 Windows: Show compiler invocation
  0ea37df meson: store ARM SIMD and NEON tests as text files
  2065a07 meson: simplify and fix mmx library compilation
  6e206cf meson: Add proper include paths for the loongson check
  9ed0576 meson: fix copy-n-paste error for arm simd assembly
  d13f6a8 meson: fix typo which breaks loongson checks
  e7ac62c meson: work around meson issue #5115

Signed-off-by: Yousong Zhou <redacted>