Valve's patches add use of "ceil" without using libm, it works
by accident with -O2 but fails with -Os.

ld: dlls/winevulkan/vulkan.o: in function `fshack_vk_queue_present':
vulkan.c:(.text+0x12f46): undefined reference to `ceil'
--- a/dlls/winevulkan/Makefile.in
+++ b/dlls/winevulkan/Makefile.in
@@ -4,3 +4,3 @@
 IMPORTS   = user32 gdi32 advapi32 setupapi win32u
-EXTRALIBS = $(PTHREAD_LIBS)
+EXTRALIBS = -lm $(PTHREAD_LIBS)