Add support for static linking of sqlx

`sqlx` requires linking against OpenSSL twice:

- `sqlx-macros` needs to link against OpenSSL as a shared libary for use
  at compile time.
- `sqlx` needs to link against OpenSSL a static library for use at
  runtime.

You can find the details here:

launchbadge/sqlx#670
sfackler/rust-openssl#1337

We go with the fix proposed by @sfackler, and add a test program that we
can use to verify everything works correctly.

We remove a few `OPENSSL`-related variables that were added 4 years ago,
and that no longer appear to be needed.

Dockerfile

@@ -67,7 +67,7 @@ RUN apt-get update && \
     curl -fLO https://github.com/EmbarkStudios/cargo-deny/releases/download/$CARGO_DENY_VERSION/cargo-deny-$CARGO_DENY_VERSION-x86_64-unknown-linux-musl.tar.gz && \
     tar xf cargo-deny-$CARGO_DENY_VERSION-x86_64-unknown-linux-musl.tar.gz && \
     mv cargo-deny-$CARGO_DENY_VERSION-x86_64-unknown-linux-musl/cargo-deny /usr/local/bin/ && \
-    rm -rf cargo-deny-$CARGO_DENY_VERSION-x86_64-unknown-linux-musl cargo-deny-$CARGO_DENY_VERSION-x86_64-unknown-linux-musl.tar.gz 
+    rm -rf cargo-deny-$CARGO_DENY_VERSION-x86_64-unknown-linux-musl cargo-deny-$CARGO_DENY_VERSION-x86_64-unknown-linux-musl.tar.gz
 
 # Static linking for C++ code
 RUN sudo ln -s "/usr/bin/g++" "/usr/bin/musl-g++"
@@ -142,11 +142,8 @@ RUN echo "Building libpq" && \
     cd ../../bin/pg_config && make && sudo make install && \
     rm -r /tmp/*
 
-ENV OPENSSL_DIR=/usr/local/musl/ \
-    OPENSSL_INCLUDE_DIR=/usr/local/musl/include/ \
-    DEP_OPENSSL_INCLUDE=/usr/local/musl/include/ \
-    OPENSSL_LIB_DIR=/usr/local/musl/lib/ \
-    OPENSSL_STATIC=1 \
+ENV X86_64_UNKNOWN_LINUX_MUSL_OPENSSL_DIR=/usr/local/musl/ \
+    X86_64_UNKNOWN_LINUX_MUSL_OPENSSL_STATIC=1 \
     PQ_LIB_STATIC_X86_64_UNKNOWN_LINUX_MUSL=1 \
     PG_CONFIG_X86_64_UNKNOWN_LINUX_GNU=/usr/bin/pg_config \
     PKG_CONFIG_ALLOW_CROSS=true \

README.md

@@ -2,6 +2,8 @@
 
 [![Docker Image](https://img.shields.io/docker/pulls/ekidd/rust-musl-builder.svg?maxAge=2592000)](https://hub.docker.com/r/ekidd/rust-musl-builder/)
 
+[Source on GitHub](https://github.com/emk/rust-musl-builder)
+
 ## What is this?
 
 Do you want to compile a completely static Rust binary with no external dependencies?  If so, try:
@@ -13,7 +15,7 @@ rust-musl-builder cargo build --release
 
 This command assumes that `$(pwd)` is readable and writable by uid 1000, gid 1000. At the moment, it doesn't attempt to cache libraries between builds, so this is best reserved for making final release builds.
 
-For a more realistic example, see the `Dockerfile` for [examples/using-diesel](./examples/using-diesel).
+For a more realistic example, see the `Dockerfile` for [examples/using-diesel](./examples/using-diesel) [examples/using-sqlx](./examples/using-sqlx).
 
 ## Deploying your Rust application
 
@@ -36,7 +38,7 @@ In general, we provide the following tagged Docker images:
   Rust, please file an issue.
 
 At a minimum, each of these images should be able to
-compile [examples/using-diesel](./examples/using-diesel).
+compile [examples/using-diesel](./examples/using-diesel) and [examples/using-sqlx](./examples/using-sqlx).
 
 [comp]: https://rust-lang.github.io/rustup-components-history/index.html
 
@@ -94,8 +96,6 @@ This image also supports the following extra goodies:
 If your application uses OpenSSL, you will also need to take a few extra steps to make sure that it can find OpenSSL's list of trusted certificates, which is stored in different locations on different Linux distributions. You can do this using [`openssl-probe`](https://crates.io/crates/openssl-probe) as follows:
 
 ```rust
-extern crate openssl_probe;
-
 fn main() {
     openssl_probe::init_ssl_cert_env_vars();
     //... your code

examples/using-diesel/Cargo.toml

@@ -9,3 +9,4 @@ diesel = { version = "1", features = ["postgres", "sqlite"] }
 libsqlite3-sys = { version = "*", features = ["bundled"] }
 # Needed for Postgres.
 openssl = "*"
+openssl-probe = "0.1.2"

examples/using-diesel/src/main.rs

@@ -46,6 +46,8 @@ where
 }
 
 fn main() {
+    openssl_probe::init_ssl_cert_env_vars();
+
     println!("Hello, world!");
 
     // Only run our database example if we have a database. Otherwise, we just

examples/using-sqlx/.dockerignore

@@ -0,0 +1 @@
+target