Cleanup docs Dockerfile, so it matches best practices.

Docker-DCO-1.1-Signed-off-by: Joseph Ferguson <joe@infosiftr.com> (github: yosifkit)
Revert "Use code generation to set IAMSTATIC instead of -X"

This reverts commit 3e10b93106dea94e5747ab32fe4ac765aa22f9bc.

Conflicts:
	.gitignore
	hack/make.sh
	hack/make/dynbinary

Docker-DCO-1.1-Signed-off-by: Jessica Frazelle <jess@docker.com> (github: jfrazelle)
Merge pull request #8717 from yosifkit/docs-dockerfile

Cleanup docs Dockerfile, so it matches best practices.
Revert "use code generation for GITCOMMIT/VERSION too"

This reverts commit 85744a35de0e30c2dd6741b833f38ff218c8a3fc.

Conflicts:
	.gitignore
	hack/make.sh

Docker-DCO-1.1-Signed-off-by: Jessica Frazelle <jess@docker.com> (github: jfrazelle)
Revert "finally, use code generation for INITSHA1 & INITPATH too"

This reverts commit c7c620dd9fce0e7b437ee185c7a58341f3b8e3aa.

Conflicts:
	.gitignore
	hack/make.sh
	hack/make/dynbinary

Docker-DCO-1.1-Signed-off-by: Jessica Frazelle <jess@docker.com> (github: jfrazelle)
Merge pull request #8833 from jfrazelle/revert-gccgo-changes

Revert gccgo changes