eclass: meson: Update generated machine files for deprecated "pkgconfig" field

Meson release 1.3.0 has deprecated the use of "pkgconfig" field in
machine (native/cross build) files. Defining the old "pkgconfig" and the
new "pkg-config" fields simultaneously is recommended for
forward+backwrd compat. and silences the deprecation notice.

See meson changelog for deprecation notice:
https://mesonbuild.com/Release-notes-for-1-3-0.html#machine-files-pkgconfig-field-deprecated-and-replaced-by-pkgconfig

BUG=None
TEST=emerge virglrenderer

Change-Id: I91684f142f9d4613a5c0401a243b6c2972cd2610
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/eclass-overlay/+/5447238
Reviewed-by: Allen Webb <allenwebb@google.com>
Tested-by: Ryan Neph <ryanneph@google.com>
Commit-Queue: Ryan Neph <ryanneph@google.com>
diff --git a/eclass/meson.eclass b/eclass/meson.eclass
index b601c38..70eca21 100644
--- a/eclass/meson.eclass
+++ b/eclass/meson.eclass
@@ -188,6 +188,7 @@
 	objcopy = $(_meson_env_array "$(tc-getOBJCOPY)")
 	objcpp = $(_meson_env_array "$(tc-getPROG OBJCXX c++)")
 	pkgconfig = '$(tc-getPKG_CONFIG)'
+	pkg-config = '$(tc-getPKG_CONFIG)'
 	strip = $(_meson_env_array "$(tc-getSTRIP)")
 	windres = $(_meson_env_array "$(tc-getRC)")
 
@@ -245,6 +246,7 @@
 	objcopy = $(_meson_env_array "$(tc-getBUILD_OBJCOPY)")
 	objcpp = $(_meson_env_array "$(tc-getBUILD_PROG OBJCXX c++)")
 	pkgconfig = '$(tc-getBUILD_PKG_CONFIG)'
+	pkg-config = '$(tc-getBUILD_PKG_CONFIG)'
 	strip = $(_meson_env_array "$(tc-getBUILD_STRIP)")
 	windres = $(_meson_env_array "$(tc-getBUILD_PROG RC windres)")