internal/build:compile with c mode,when c file

runtime/internal/clite/os/_os/os.c

@@ -1,8 +1,6 @@
 #include <stdlib.h>
 #include <errno.h>
 
-extern "C" {
-
 int cliteClearenv()
 {
 	extern char **environ;
@@ -14,5 +12,3 @@ int cliteClearenv()
 }
 
 int cliteErrno() { return errno; }
-
-}

runtime/internal/clite/os/os_darwin.go

@@ -23,7 +23,7 @@ import (
 )
 
 const (
-	LLGoFiles   = "_os/os.cpp"
+	LLGoFiles   = "_os/os.c"
 	LLGoPackage = "link"
 )
 

runtime/internal/clite/os/os_other.go

@@ -25,7 +25,7 @@ import (
 )
 
 const (
-	LLGoFiles   = "_os/os.cpp"
+	LLGoFiles   = "_os/os.c"
 	LLGoPackage = "link"
 )