KVM: selftests: add -MP to CFLAGS

Using -MD without -MP causes build failures when a header file is deleted
or moved. With -MP, the compiler will emit phony targets for the header
files it lists as dependencies, and the Makefiles won't refuse to attempt
to rebuild a C unit which no longer includes the deleted header.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Link: https://lore.kernel.org/r/9fc8b5395321abbfcaf5d78477a9a7cd350b08e4.camel@infradead.org
Signed-off-by: Sean Christopherson <seanjc@google.com>

tools/testing/selftests/kvm/Makefile

@@ -226,7 +226,7 @@ else
 LINUX_TOOL_ARCH_INCLUDE = $(top_srcdir)/tools/arch/$(ARCH)/include
 endif
 CFLAGS += -Wall -Wstrict-prototypes -Wuninitialized -O2 -g -std=gnu99 \
-	-Wno-gnu-variable-sized-type-not-at-end -MD\
+	-Wno-gnu-variable-sized-type-not-at-end -MD -MP \
 	-fno-builtin-memcmp -fno-builtin-memcpy -fno-builtin-memset \
 	-fno-builtin-strnlen \
 	-fno-stack-protector -fno-PIE -I$(LINUX_TOOL_INCLUDE) \