rework build system

Cargo.toml

@@ -28,3 +28,6 @@ libc = "0.2"
 crc = "1.8"
 hex-literal = "0.2"
 getrandom = "0.1"
+
+[build-dependencies]
+rustc_version = "0.2"

Makefile

@@ -5,11 +5,8 @@ CLI:= cli
 
 PROJECT=khash
 
-BUILD:=./target/release
-DEBUG:=./target/debug
-
-.PHONY: $(PROJECT)
-$(PROJECT): release
+BUILD =target/release
+DEBUG =target/debug
 
 .PHONY: release
 release: $(BUILD)/lib$(PROJECT).so
@@ -17,6 +14,9 @@ release: $(BUILD)/lib$(PROJECT).so
 .PHONY: debug
 debug: $(DEBUG)/lib$(PROJECT).so
 
+.PHONY: $(PROJECT)
+$(PROJECT): $(BUILD)/lib$(PROJECT).so
+
 $(BUILD)/lib$(PROJECT).so: RUSTFLAGS?= -C target-cpu=native 
 $(BUILD)/lib$(PROJECT).so:
 	RUSTFLAGS="$(RUSTFLAGS)" cargo build --release
@@ -39,7 +39,7 @@ test: | clean
 	cd $(CLI) && $(MAKE) test
 
 clean:
-	rm -f $(BUILD)/lib
+	rm -f {$(BUILD),$(DEBUG)}/lib*
 	cd $(CLI) && make clean
 
 install:

build.rs

@@ -0,0 +1,24 @@
+
+extern crate rustc_version;
+use rustc_version::{version, version_meta, Channel};
+
+fn main() {
+    // Assert we haven't travelled back in time
+    assert!(version().unwrap().major >= 1);
+
+    // Set cfg flags depending on release channel
+    match version_meta().unwrap().channel {
+        Channel::Stable => {
+            println!("cargo:rustc-cfg=stable");
+        }
+        Channel::Beta => {
+            println!("cargo:rustc-cfg=beta");
+        }
+        Channel::Nightly => {
+            println!("cargo:rustc-cfg=nightly");
+        }
+        Channel::Dev => {
+            println!("cargo:rustc-cfg=dev");
+        }
+    }
+}