meson: fix gtk-doc invocations

It assumes the tools are python scripts, but we create .exe launchers

mingw-w64-meson/0004-fix-gtk-doc.patch

@@ -0,0 +1,11 @@
+--- meson-0.55.1/mesonbuild/scripts/gtkdochelper.py.orig	2020-08-15 18:27:05.000000000 +0200
++++ meson-0.55.1/mesonbuild/scripts/gtkdochelper.py	2020-08-21 14:48:07.741232700 +0200
+@@ -64,7 +64,7 @@
+             library_paths.extend(env['LD_LIBRARY_PATH'].split(os.pathsep))
+         env['LD_LIBRARY_PATH'] = os.pathsep.join(library_paths)
+ 
+-    if is_windows():
++    if is_windows() and not shutil.which(cmd[0]):
+         cmd.insert(0, sys.executable)
+ 
+     # Put stderr into stdout since we want to print it out anyway.

mingw-w64-meson/PKGBUILD

@@ -4,7 +4,7 @@ _realname=meson
 pkgbase=mingw-w64-${_realname}
 pkgname="${MINGW_PACKAGE_PREFIX}-${_realname}"
 pkgver=0.55.1
-pkgrel=1
+pkgrel=2
 pkgdesc="High-productivity build system (mingw-w64)"
 arch=('any')
 url="https://mesonbuild.com/"
@@ -17,11 +17,13 @@ source=("https://github.com/mesonbuild/${_realname}/releases/download/${pkgver}/
         'color-term.patch'
         '0002-Default-to-sys.prefix-as-the-default-prefix.patch'
         '0003-Strip-the-prefix-from-all-paths-when-installing-with.patch'
+        '0004-fix-gtk-doc.patch'
         'install-man.patch')
 sha256sums=('3b5741f884e04928bdfa1947467ff06afa6c98e623c25cef75adf71ca39ce080'
             '5805aed0a117536eb16dd8eef978c6be57c2471b655ede63e25517c28b4f4cf0'
             '363182db7e7059526353278966aa4704e8a26cbaf7c3b7dc5d6e4f01692a40e6'
             '2093c617cf3146a4cea601e7c73400d8ec5fd52ac5cf642c4f5af2d6493b1cb1'
+            'ca14c322dd18e7c0614fda1ec8ba42ba5148305e641612e0290e4a350c042adf'
             '0682a36cb75e545a78b81293303835a16171f25baf949905dc08029436efff84')
 
 prepare() {
@@ -30,6 +32,7 @@ prepare() {
   patch -Np1 -i "${srcdir}"/color-term.patch
   patch -Np1 -i "${srcdir}"/0002-Default-to-sys.prefix-as-the-default-prefix.patch
   patch -Np1 -i "${srcdir}"/0003-Strip-the-prefix-from-all-paths-when-installing-with.patch
+  patch -Np1 -i "${srcdir}"/0004-fix-gtk-doc.patch
   patch -Np1 -i "${srcdir}"/install-man.patch
 }