Use libiberty's lrealpath to avoid portability problems.

The dmd front-end function FileName::canonicalName could be called
during the semantic pass of import("file") expressions, so still
requires that realpath() be redefined.

Initial patch by Rainer Orth.

gcc/d/ChangeLog:

2019-03-12  Iain Buclaw  <ibuclaw@gdcproject.org>

	PR d/87866
	* d-system.h (realpath): Redefine as lrealpath.

From-SVN: r269619

gcc/d/ChangeLog

 2019-03-12  Iain Buclaw  <ibuclaw@gdcproject.org>
 
+	PR d/87866
+	* d-system.h (realpath): Redefine as lrealpath.
+
+2019-03-12  Iain Buclaw  <ibuclaw@gdcproject.org>
+
 	* d-lang.cc (d_init_options): Set global.params.cplusplus to C++14.
 	* d-target.cc (Target::cppFundamentalType): New method.
 

gcc/d/d-system.h

@@ -31,6 +31,10 @@
 #undef assert
 #define assert(EXPR) gcc_assert(EXPR)
 
+/* Use libiberty's lrealpath to avoid portability problems.  */
+#undef realpath
+#define realpath(a, b) lrealpath((a))
+
 /* Forward ctype.h macros used by the dmd front-end to safe-ctype.h.  */
 #undef isalpha
 #define isalpha(c) ISALPHA(c)