fix: fix building libz-sys (#420)

Author: FelixMoelder

.github/workflows/rust.yml

@@ -85,9 +85,6 @@ jobs:
         target:
           - no-default-features
           - all-features
-          - musl-release-no-default-features
-          - musl-release-all-features
-          - musl-all-features
         include:
           - target: no-default-features
             args: --no-default-features
@@ -96,18 +93,6 @@ jobs:
             args: --all-features
             toolchain_target: x86_64-unknown-linux-musl
             use_cross: false
-          - target: musl-release-no-default-features
-            args: --release --target x86_64-unknown-linux-musl --no-default-features
-            toolchain_target: x86_64-unknown-linux-musl
-            use_cross: true
-          - target: musl-release-all-features
-            args: --release --target x86_64-unknown-linux-musl --all-features --verbose
-            toolchain_target: x86_64-unknown-linux-musl
-            use_cross: true
-          - target: musl-all-features
-            args: --target x86_64-unknown-linux-musl --all-features --verbose
-            toolchain_target: x86_64-unknown-linux-musl
-            use_cross: true
 
     steps:
       - name: Checkout repository

Cargo.toml

@@ -16,6 +16,7 @@ pre-release-commit-message = "release version {{version}}"
 tag-message = "Version {{version}} of Rust-HTSlib."
 
 [dependencies]
+libz-sys = ">=1.1.15"
 bio-types = ">=0.9"
 byteorder = "1.3"
 custom_derive = "0.1"

Cross.toml

@@ -22,36 +22,6 @@ If you only want to use the library, there is no need to clone the repository. G
 
 rust-htslib comes with pre-built bindings to htslib for Mac and Linux. You will need a C toolchain compatible with the `cc` crate. The build script for this crate will automatically build a link htslib.
 
-
-### MUSL build
-To compile this for MUSL crate you need docker and cross:
-
-```shell
-$ cargo install cross
-$ cross build 				              # will build with GNU GCC or LLVM toolchains
-```
-
-If you want to run rust-htslib code on AWS lambda, [you'll need to statically compile it with MUSL](https://github.com/awslabs/aws-lambda-rust-runtime/issues/17#issuecomment-577490373) as follows:
-
-```shell
-$ cross build --target x86_64-unknown-linux-musl      # will build with MUSL toolchain
-```
-
-Alternatively, you can also install it locally by installing the development headers of zlib, bzip2 and xz. For instance, in Debian systems one needs the following dependencies:
-
-```shell
-$ sudo apt-get install zlib1g-dev libbz2-dev liblzma-dev clang pkg-config
-```
-
-We provide Dockerfile bases that provide these dependencies. Refer to the [docker](https://github.com/rust-bio/rust-htslib/tree/master/docker) directory in this repository for the latest instructions, including LLVM installation.
-
-On OSX:
-
-```shell
-$ brew install FiloSottile/musl-cross/musl-cross
-$ brew install bzip2 zlib xz curl-openssl
-```
-
 ## Usage
 
 Add this to your `Cargo.toml`: