add inline assembly support

std/bootstrap.zig

@@ -0,0 +1,16 @@
+
+// TODO conditionally compile this differently for non-ELF
+#attribute("naked")
+export fn _start() -> unreachable {
+    // TODO conditionally compile this differently for other architectures and other OSes
+    asm volatile ("
+        mov (%%rsp), %%rdi              // first parameter is argc
+        lea 0x8(%%rsp), %%rsi           // second parameter is argv
+        lea 0x10(%%rsp,%%rdi,8), %%rdx  // third paremeter is env
+        callq main
+        mov %%rax, %%rdi                // return value is the parameter to exit syscall
+        mov $60, %%rax                  // 60 is exit syscall number
+        syscall
+    ");
+    unreachable
+}