Add a sorry excuse for a README

README.md

+# Segatools
+
+Quick start on a Linux build host:
+
+```
+# Install Meson and a recent build of MinGW-w64, then:
+
+$ meson --cross cross-build-32.txt _build32
+$ ninja -C _build32
+$ meson --cross cross-build-64.txt
+$ ninja -C _build64
+```
+
+Building on MSYS2 is also possible; consult Meson documentation for details.
+
+Additional documentation will be forthcoming.