Update building instructions

BUILDING.md

@@ -2,18 +2,50 @@
 
 ## Using Cargo
 
+A debug build is straightforward:
+
 ```bash
 cargo build
 ```
 
+A release build is also straightforward:
+
+```bash
+cargo build --release
+```
+
+If you want to install the binary locally from source:
+
+```bash
+# Where you are currently an the root of the project
+cargo install --path .
+```
+
 ## Completely static binary
 
 To compile a completely static binary (not linked to libc), we need to target
 musl using:
 
 ```bash
+rustup target add x86_64-unknown-linux-musl
 cargo build --target x86_64-unknown-linux-musl
 ```
 
+### Mac-specific
+
+Note that on Mac OS X you will need to install musl-gcc:
+
+```bash
+brew install FiloSottile/musl-cross/musl-cross
+```
+
+And to do a strip (on Mac), use the musl strip:
+
+```bash
+x86_64-linux-musl-gcc target/x86_64-unknown-linux-musl/release/distant
+```
+
 At the moment, this is not possible to build on M1 Macs: 
 https://github.com/FiloSottile/homebrew-musl-cross/issues/23
+
+