Add support for pgm and epgm

Cargo.toml

@@ -24,6 +24,7 @@ default = ["zmq_has"]
 # this feature is a no-op and only present for backward-compatibility;
 # it will be removed in the next API-breaking release.
 zmq_has = []
+libpgm = ["zmq-sys/libpgm"]
 
 [dependencies]
 bitflags = "1.0"

zmq-sys/Cargo.toml

@@ -14,6 +14,7 @@ build = "build/main.rs"
 links = "zmq"
 
 [features]
+libpgm = []
 
 [dependencies]
 libc = "0.2.15"

zmq-sys/build/main.rs

@@ -1,13 +1,27 @@
+use std::env;
+
 pub fn configure() {
     println!("cargo:rerun-if-changed=build/main.rs");
     println!("cargo:rerun-if-env-changed=PROFILE");
 
+    let maybe_libpgm = if cfg!(feature = "libpgm") {
+        let lib_dir = env::var("DEP_PGM_LIB")
+            .expect("build metadata `DEP_PGM_LIB` required");
+        let include_dir = env::var("DEP_PGM_INCLUDE")
+            .expect("build metadata `DEP_PGM_INCLUDE` required");
+
+        Some(zeromq_src::LibLocation::new(lib_dir, include_dir))
+    } else {
+        None
+    };
+
     // Note that by default `libzmq` builds without `libsodium` by instead
     // relying on `tweetnacl`. However since this `tweetnacl` [has never been
     // audited nor is ready for production](https://github.com/zeromq/libzmq/issues/3006),
     // we link against `libsodium` to enable `ZMQ_CURVE`.
     zeromq_src::Build::new()
         .with_libsodium(None)
+        .with_libpgm(maybe_libpgm)
         .build();
 }