Makefile: Only include cc_platform.mk when not using runc_nodmz

One of the reasons to have a build tag to disable runc-dmz is to get rid
of possible compile issues introduced by it (it needs to cross-compile a
C program).

We were not being strict enough to include this file only when needed.
This patch includes it only when not using runc_nodmz.

While we want to fix the compilation issues of runc-dmz in another
commit, let's make when using runc_nodmz we don't include more than
needed to compile.

Signed-off-by: Rodrigo Campos <[email protected]>

Makefile

@@ -3,9 +3,6 @@ SHELL = /bin/bash
 CONTAINER_ENGINE := docker
 GO ?= go
 
-# Get CC values for cross-compilation.
-include cc_platform.mk
-
 PREFIX ?= /usr/local
 BINDIR := $(PREFIX)/sbin
 MANDIR := $(PREFIX)/share/man
@@ -17,6 +14,12 @@ PROJECT := github.com/opencontainers/runc
 BUILDTAGS ?= seccomp urfave_cli_no_docs
 BUILDTAGS += $(EXTRA_BUILDTAGS)
 
+# Only include the CC values for cross-compilation when the runc_nodmz build tag is not set.
+# We want to leave everything as untouched as possible when it is not set.
+ifneq (runc_nodmz,$(filter runc_nodmz, $(BUILDTAGS)))
+include cc_platform.mk
+endif
+
 COMMIT ?= $(shell git describe --dirty --long --always)
 VERSION ?= $(shell cat ./VERSION)
 LDFLAGS_COMMON := -X main.gitCommit=$(COMMIT) -X main.version=$(VERSION)