Makefile: list sources via find conditionally

Taken directly from podman's repository. The current list of sources
doesn't list vendor sources and therefore if you need to make changes to
vendor for testing a backport or anything else, it's required to
modify the Makefile before attempting to do so. Since we don't list
the sources manually anymore, don't do makefile source validation check.

Signed-off-by: Danish Prakash <[email protected]>

Makefile

@@ -41,7 +41,12 @@ LIBSECCOMP_COMMIT := release-2.3
 
 EXTRA_LDFLAGS ?=
 BUILDAH_LDFLAGS := $(GO_LDFLAGS) '-X main.GitCommit=$(GIT_COMMIT) -X main.buildInfo=$(SOURCE_DATE_EPOCH) -X main.cniVersion=$(CNI_COMMIT) $(EXTRA_LDFLAGS)'
-SOURCES=*.go imagebuildah/*.go bind/*.go chroot/*.go copier/*.go define/*.go docker/*.go internal/config/*.go internal/mkcw/*.go internal/mkcw/types/*.go internal/parse/*.go internal/sbom/*.go internal/source/*.go internal/tmpdir/*.go internal/*.go internal/util/*.go internal/volumes/*.go manifests/*.go pkg/binfmt/*.go pkg/blobcache/*.go pkg/chrootuser/*.go pkg/cli/*.go pkg/completion/*.go pkg/formats/*.go pkg/jail/*.go pkg/overlay/*.go pkg/parse/*.go pkg/rusage/*.go pkg/sshagent/*.go pkg/umask/*.go pkg/util/*.go pkg/volumes/*.go util/*.go
+
+# This isn't what we actually build; it's a superset, used for target
+# dependencies. Basically: all *.go and *.c files, except *_test.go,
+# and except anything in a dot subdirectory. If any of these files is
+# newer than our target (bin/buildah), a rebuild is triggered.
+SOURCES=$(shell find . -path './.*' -prune -o \( \( -name '*.go' -o -name '*.c' \) -a ! -name '*_test.go' \) -print)
 
 LINTFLAGS ?=
 
@@ -136,7 +141,6 @@ validate: install.tools
 	./tests/validate/whitespace.sh
 	./hack/xref-helpmsgs-manpages
 	./tests/validate/pr-should-include-tests
-	./hack/makefile_sources
 
 .PHONY: install.tools
 install.tools: