vdrift: fix glibc build

Fixes #7775

srcpkgs/vdrift/patches/glibc-2.26-assert.patch

@@ -0,0 +1,40 @@
+--- src/bezier.cpp.orig	2014-08-11 18:08:01.000000000 +0000
++++ src/bezier.cpp	2017-09-22 19:42:14.914232067 +0000
+@@ -463,7 +463,7 @@
+ 
+ void Bezier::ReadFrom(std::istream &openfile)
+ {
+-	assert(openfile);
++	assert(static_cast<bool>(openfile));
+ 
+ 	for (int x = 0; x < 4; x++)
+ 	{
+@@ -480,7 +480,7 @@
+ 
+ void Bezier::ReadFromYZX(std::istream &openfile)
+ {
+-	assert(openfile);
++	assert(static_cast<bool>(openfile));
+ 	for (int x = 0; x < 4; x++)
+ 	{
+ 		for (int y = 0; y < 4; y++)
+@@ -494,7 +494,7 @@
+ 
+ void Bezier::WriteTo(std::ostream &openfile) const
+ {
+-	assert(openfile);
++	assert(static_cast<bool>(openfile));
+ 
+ 	for (int x = 0; x < 4; x++)
+ 	{
+--- src/roadstrip.cpp.orig	2014-08-01 06:18:06.000000000 +0000
++++ src/roadstrip.cpp	2017-09-22 19:44:11.794238097 +0000
+@@ -31,7 +31,7 @@
+ 	bool reverse,
+ 	std::ostream & error_output)
+ {
+-	assert(openfile);
++	assert(static_cast<bool>(openfile));
+ 
+ 	int num = 0;
+ 	openfile >> num;