Unix rtlib: Fix exec() to support spaces in executable path

fb_hGetShortPath() escaped spaces as "\ " in paths containing spaces,
which is bad here because the path is passed to execvp() which is not
a shell but just expects the raw file name.

On top of that, the fb_hConvertPath() done afterwards converts \ to /,
so spaces were turned into "/ ", resulting in a completely different path
than what was given to exec().

This fixes the former, so the second won't kick in in this case either
anymore, but the \ => / conversion in general is not removed here. That's
another discussion...

changelog.txt

@@ -25,6 +25,7 @@ Version 1.06.0
 - boolean initializer values for global or static variables were not emitted properly
 - Compiler crash after reporting error about REDIM on a fixed-size array field
 - #827: Using the GNU gold linker (instead of ld.bfd) resulted in broken binaries due to fbextra.x, which fbc uses with ld.bfd to discard the objinfo .fbctinf sections, but is not supported by gold. Now when gold is detected, fbextra.x won't be used anymore, in order to get working binaries.
+- exec() on Linux & co was broken with regards to spaces in the executable path. Spaces were converted to "\ " and then to "/ ", resulting in a different path than given.
 
 
 Version 1.05.0

src/rtlib/unix/sys_execex.c

@@ -16,7 +16,8 @@ FBCALL int fb_ExecEx( FBSTRING *program, FBSTRING *args, int do_fork )
 		return -1;
 	}
 
-	fb_hGetShortPath( program->data, buffer, MAX_PATH );
+	strncpy( buffer, program->data, sizeof( buffer ) );
+	buffer[sizeof( buffer ) - 1] = 0;
 
 	fb_hConvertPath( buffer );