use __FILE__, not __BASE_FILE__

The intention was to use the file's basename, but __BASE_FILE__ means "the root
file that is being parsed and contains #include statements".

If we had a function using __BASE_FILE__ and that was defined in an #included
file, __BASE_FILE__ would indicate the first file where the #include is, and
not the file where the function is defined. __BASE_FILE__ works for us because
we don't ever include function definitions that log something, so __BASE_FILE__
always coincides with __FILE__ for our logging; but still __BASE_FILE__ is
semantically the wrong constant.

Related: OS#2740
Change-Id: Ibc1d3746f1876ac42d6b1faf0e5f83bd2283cdcc
diff --git a/include/osmocom/core/utils.h b/include/osmocom/core/utils.h
index dd4461c..e2d5134 100644
--- a/include/osmocom/core/utils.h
+++ b/include/osmocom/core/utils.h
@@ -78,7 +78,7 @@
  */
 #define OSMO_ASSERT(exp)    \
 	if (!(exp)) { \
-		osmo_panic("Assert failed %s %s:%d\n", #exp, __BASE_FILE__, __LINE__); \
+		osmo_panic("Assert failed %s %s:%d\n", #exp, __FILE__, __LINE__); \
 	}
 
 /*! duplicate a string using talloc and release its prior content (if any)