Make cross-compilation scripts work from MSYS2

This is weird and runs very slowly.

Meson can also find libraries outside the subroot,
in particular the fast float plugin.

README.adoc

@@ -64,7 +64,7 @@ from a context menu.
 Windows
 ~~~~~~~
 'fiv' can be cross-compiled for Windows, provided that you install a bunch of
-dependencies listed at the beginning of 'msys2-cross-configure.sh',
+dependencies listed at the beginning of 'msys2-configure.sh',
 plus rsvg-convert from librsvg2, and icotool from icoutils.
 Beware that the build will take up about a gigabyte of disk space.
 

meson.build

@@ -326,10 +326,11 @@ if not win32
 		meson.add_install_script(updater, skip_if_destdir : dynamic_desktops)
 	endif
 elif meson.is_cross_build()
+	# Note that even compiling /from within MSYS2/ can still be a cross-build.
 	msys2_root = meson.get_external_property('msys2_root')
-	meson.add_install_script('msys2-cross-install.sh', msys2_root)
+	meson.add_install_script('msys2-install.sh', msys2_root)
 
-	# This is the minimum to run targets from msys2-cross-configure.sh builds.
+	# This is the minimum to run targets from msys2-configure.sh builds.
 	meson.add_devenv({
 		'WINEPATH' : msys2_root / 'bin',
 		'XDG_DATA_DIRS' : msys2_root / 'share',

msys2-configure.sh

@@ -1,9 +1,16 @@
 #!/bin/sh -e
-# msys2-cross-configure.sh: set up an MSYS2-based cross-compiled Meson build.
+# msys2-configure.sh: set up an MSYS2-based Meson build targeting x86-64.
 # Dependencies: AWK, sed, sha256sum, cURL, bsdtar,
 # wine64, Meson, mingw-w64-binutils, mingw-w64-gcc, pkg-config
 repository=https://repo.msys2.org/mingw/mingw64/
 
+# Support running directly from within MSYS2 on Windows.
+if [ -n "$MSYSTEM" ]
+then
+	wine64() { "$@"; }
+	awk() { command awk -v RS='\r?\n' "$@"; }
+fi
+
 status() {
 	echo "$(tput bold)-- $*$(tput sgr0)"
 }
@@ -74,6 +81,8 @@ configure() {
 
 setup() {
 	status Setting up Meson
+	[ -n "$MSYSTEM" ] && wrap=false || wrap=true
+
 	cat >"$toolchain" <<-EOF
 	[binaries]
 	c = 'x86_64-w64-mingw32-gcc'
@@ -88,7 +97,7 @@ setup() {
 	sys_root = '$builddir'
 	msys2_root = '$msys2_root'
 	pkg_config_libdir = '$msys2_root/share/pkgconfig:$msys2_root/lib/pkgconfig'
-	needs_exe_wrapper = true
+	needs_exe_wrapper = $wrap
 
 	[host_machine]
 	system = 'windows'

msys2-install.sh

@@ -3,6 +3,13 @@ export LC_ALL=C
 cd "$MESON_INSTALL_DESTDIR_PREFIX"
 msys2_root=$1
 
+# Support running directly from within MSYS2 on Windows.
+if [ -n "$MSYSTEM" ]
+then
+	wine64() { "$@"; }
+	awk() { command awk -v RS='\r?\n' "$@"; }
+fi
+
 # Copy binaries we directly or indirectly depend on.
 cp -p "$msys2_root"/bin/*.dll .
 cp -p "$msys2_root"/bin/wperl.exe .