infrastructure for reproducible builds (#3770)

* Add deterministic buildsystem

* Update CircleCI config

* Enable build on all branches for testing purposes

* Revert "Enable build on all branches for testing purposes"

This reverts commit bf5cf66da9.

* Remove develop from branch filters

* Remove dangling reference to develop

* Upload binaries too

* Build for stable branches too

scripts/gitian-keys/README.md

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+## PGP keys of Gitian builders and Tendermint Developers
+
+The file `keys.txt` contains fingerprints of the public keys of Gitian builders
+and active developers.
+
+The associated keys are mainly used to sign git commits or the build results
+of Gitian builds.
+
+The most recent version of each pgp key can be found on most PGP key servers.
+
+Fetch the latest version from the key server to see if any key was revoked in
+the meantime.
+To fetch the latest version of all pgp keys in your gpg homedir,
+
+```sh
+gpg --refresh-keys
+```
+
+To fetch keys of Gitian builders and active core developers, feed the list of
+fingerprints of the primary keys into gpg:
+
+```sh
+while read fingerprint keyholder_name; \
+do gpg --keyserver hkp://subset.pool.sks-keyservers.net \
+--recv-keys ${fingerprint}; done < ./keys.txt
+```
+
+Add your key to the list if you are a Tendermint core developer or you have
+provided Gitian signatures for two major or minor releases of Tendermint.

scripts/gitian-keys/keys.txt

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+04160004A8276E40BB9890FBE8A48AE5311D765A Alessio Treglia