msys2-runtime: build for cygwin

In theory this means the "0001-Add-MSYS2-triplet.patch" patch
can be dropped.

msys2-runtime/PKGBUILD

@@ -4,7 +4,7 @@
 pkgbase=msys2-runtime
 pkgname=('msys2-runtime' 'msys2-runtime-devel')
 pkgver=3.6.3
-pkgrel=2
+pkgrel=3
 pkgdesc="Cygwin POSIX emulation engine"
 arch=('x86_64')
 url="https://www.cygwin.com/"
@@ -214,10 +214,11 @@ build() {
 
   (cd "${srcdir}/msys2-runtime/winsup" && ./autogen.sh)
 
+  local CYGWIN_CHOST="${CHOST/-msys/-cygwin}"
   "${srcdir}"/msys2-runtime/configure \
     --with-msys2-runtime-commit="$(cat "${srcdir}/msys2-runtime.commit")" \
     --prefix=/usr \
-    --build=${CHOST} \
+    --build=${CYGWIN_CHOST} \
     --sysconfdir=/etc \
     "${extra_config[@]}"
   LC_ALL=C make
@@ -256,16 +257,17 @@ package_msys2-runtime-devel() {
   # strip breaks the split debug info.  msys2/msys2-pacman#52
   options=('!strip')
 
+  local CYGWIN_CHOST="${CHOST/-msys/-cygwin}"
   mkdir -p "${pkgdir}"/usr/bin
   cp -f "${srcdir}"/dest/usr/bin/msys-2.0.dbg "${pkgdir}"/usr/bin/
-  cp -rLf "${srcdir}"/dest/usr/${CHOST}/include "${pkgdir}"/usr/
+  cp -rLf "${srcdir}"/dest/usr/${CYGWIN_CHOST}/include "${pkgdir}"/usr/
   rm -f "${pkgdir}"/usr/include/iconv.h
   rm -f "${pkgdir}"/usr/include/unctrl.h
   # provided by libtirpc
   rm -fr "${pkgdir}"/usr/include/rpc/
 
-  cp -rLf "${srcdir}"/dest/usr/${CHOST}/lib "${pkgdir}"/usr/
+  cp -rLf "${srcdir}"/dest/usr/${CYGWIN_CHOST}/lib "${pkgdir}"/usr/
 
   # compatibility with Cygwin toolchains
-  cp "${srcdir}"/dest/usr/${CHOST}/lib/libmsys-2.0.a "${pkgdir}"/usr/lib/libcygwin.a
+  cp "${srcdir}"/dest/usr/${CYGWIN_CHOST}/lib/libmsys-2.0.a "${pkgdir}"/usr/lib/libcygwin.a
 }