ntoskrnl: Fix cross-compilation of the driver tests.

dlls/ntoskrnl.exe/tests/driver.c

@@ -75,8 +75,8 @@ static void WINAPIV ok_(const char *file, int line, int condition, const char *m
     const char *current_file;
     __ms_va_list args;
 
-    if (!(current_file = strrchr(file, '/')) &&
-        !(current_file = strrchr(file, '\\')))
+    if (!(current_file = drv_strrchr(file, '/')) &&
+        !(current_file = drv_strrchr(file, '\\')))
         current_file = file;
     else
         current_file++;

dlls/ntoskrnl.exe/tests/driver.h

@@ -35,3 +35,10 @@ struct test_input
     int winetest_debug;
     WCHAR path[1];
 };
+
+static inline char *drv_strrchr( const char *str, char ch )
+{
+    char *ret = NULL;
+    do { if (*str == ch) ret = (char *)(ULONG_PTR)str; } while (*str++);
+    return ret;
+}