Rewrite build.rs again

Makefile

@@ -31,6 +31,7 @@ endif
 
 ld := $(prefix)ld
 objdump := $(prefix)objdump
+cc := $(prefix)gcc
 
 .PHONY: all clean run iso kernel build debug_asm
 
@@ -61,7 +62,7 @@ $(kernel): kernel $(rust_os) $(assembly_object_files) $(linker_script)
 		$(assembly_object_files) $(rust_os)
 
 kernel:
-	@RUST_TARGET_PATH=$(shell pwd) xargo build --target $(target) --features "$(features)"
+	@RUST_TARGET_PATH=$(shell pwd) CC=$(cc) xargo build --target $(target) --features "$(features)"
 
 # compile assembly files
 build/arch/$(arch)/boot/%.o: $(boot_src)/%.asm

build.rs

@@ -1,16 +1,7 @@
 extern crate cc;
-use std::process::Command;
 
 fn main() {
-	let output = Command::new("uname").output()
-						 .expect("failed to get uname");
-	let compiler = match output.stdout.as_slice() {
-		b"Darwin\n" => "x86_64-elf-gcc",
-		b"Linux\n" => "gcc",
-		_ => panic!("unknown os")
-	};
     cc::Build::new()
-		.compiler(compiler)
 		.file("src/arch/x86_64/driver/apic/lapic.c")
 		.compile("cobj");
 }