Add instructions to generate static binaries

Following the discussion in containers#1478, we don't want to provide
(and maintain) static binaries, but giving instructions to
produce such builds (with appropriate warnings around these
instructions) was considered acceptable, so - here we go!

install.md

@@ -203,3 +203,32 @@ Finally, after the binary and documentation is built:
 ```bash
 sudo make install
 ```
+
+### Building a static binary
+
+Static builds of Skopeo tend to be unreliable and functionally restricted. This probably comes from the fact that some Skopeo features depend on non-Go libraries like `libgpgme` and `livdevmapper`. There has been efforts in the past to produce and maintain static builds, but the maintainers prefer to run Skopeo using distro packages or within containers.
+
+That being said, if you would like to build Skopeo statically, you might be able to do it by:
+
+- exporting environment variable `CGO_ENABLED=0` (disabling CGO causes Go to prefer native libraries when possible, instead of dynamically linking against system libraries)
+- passing the `BUILDTAGS=containers_image_openpgp` Make flag (this remove the dependency on `libgpgme` and its companion libraries)
+- commenting out the `GO_DYN_FLAGS` line in the Makefile (this flag seems to force the creation of a dynamic executable)
+
+The following command implements these steps to produce a static binary in the `bin` subdirectory of the repository:
+
+```bash
+sed 's/GO_DYN_FLAGS=/#/' Makefile |
+docker run -i -v $PWD:/src -w /src -e CGO_ENABLED=0 golang \
+make -f- BUILDTAGS=containers_image_openpgp
+```
+
+Keep in mind that the resulting binary is unsupported and might crash randomly. Only use if you know what you're doing!
+
+For more information, history, and context about static builds, check the following issues and commits:
+
+- #670
+- #755
+- #932
+- #1336
+- #1478
+- 0f458eec763626025d5146f00c3809480befe6f3