libc: Stub out setvbuf, and add S_ISREG

libs/libc/include/stdio.h

@@ -30,6 +30,10 @@ extern FILE* stdin;
 
 #define EOF -1
 
+#define _IONBF 0
+#define _IOLBF 1
+#define _IOFBF 2
+
 typedef off_t fpos_t;
 
 #ifdef __cplusplus
@@ -106,7 +110,8 @@ extern "C"
     /* Clears the error and end-of-file flags from stream. */
     void clearerr(FILE* stream);
 
-    void setbuf(FILE*, char*); // Not implemented.
+    void setbuf(FILE*, char*);              // Not implemented.
+    int setvbuf(FILE*, char*, int, size_t); // Not implemented.
 
     /* Writes formatted output according to the string format to the file stream. */
     int vfprintf(FILE* stream, const char* format, va_list ap);

libs/libc/include/sys/stat.h

@@ -12,6 +12,7 @@ struct stat // FIXME: This struct is quite stubbed out.
 };
 
 #define S_ISDIR(mode) (((mode)&0xf) == __VFS_DIRECTORY)
+#define S_ISREG(mode) (((mode)&0xf) == __VFS_FILE)
 
 #ifdef __cplusplus
 extern "C"

libs/libc/src/file.cpp

@@ -244,4 +244,9 @@ extern "C"
     {
         NOT_IMPLEMENTED("setbuf");
     }
+
+    int setvbuf(FILE*, char*, int, size_t)
+    {
+        NOT_IMPLEMENTED("setvbuf");
+    }
 }