added build-systems.md

build-systems.md

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+# Build Systems
+
+- [Make](https://www.gnu.org/software/make/) - simple classic, battle tested for decades. Even if you don't code you should know this to make sysadmin stuff easier
+- [Maven](https://maven.apache.org/) - used mainly by Java / JVM programmers, build file is XML showing its age
+- [Gradle](https://gradle.org/) - modern replacement for Maven, used mainly by Java / JVM programmers
+- [SBT](https://www.scala-sbt.org/) - used mainly by Scala programmers - my least favourite of the 3 main JVM build tools
+- [Bazel](https://bazel.build/) - incremental build system
+
+## Make
+
+See [make.md](make.md)
+
+## Maven
+
+See [maven.md](maven.md)
+
+## Gradle
+
+See [gradle.md](gradle.md)
+
+## Sbt
+
+See [sbt.md](sbt.md)
+
+## Bazel
+
+https://bazel.build/
+
+- fast incremental builds tracks changes to files and only rebuilds what is necessary
+
+### Install
+
+On Mac you'll need XCode:
+
+```shell
+xcode-select --install
+sudo xcodebuild -license accept
+```
+
+On Mac:
+
+```shell
+brew install bazel
+```
+
+Manual download:
+
+```shell
+export BAZEL_VERSION=3.2.0
+curl -fLO "https://github.com/bazelbuild/bazel/releases/download/${BAZEL_VERSION}/bazel-${BAZEL_VERSION}-installer-darwin-x86_64.sh"
+chmod +x "bazel-${BAZEL_VERSION}-installer-darwin-x86_64.sh"
+./bazel-${BAZEL_VERSION}-installer-darwin-x86_64.sh --user  # --user installs to ~/bin and sets the .bazelrc path to ~/.bazelrc
+```
+
+In [HariSekhon/DevOps-Bash-tools](devops-bash-tools.md) repo `install/` directory you can just run this instead:
+
+```shell
+install_bazel.sh  # 3.2.0  # optional version number arg
+```
+
+Check installed:
+
+```shell
+bazel version
+```
+
+Ported from private Knowledge Base page 2010+ - not sure why I didn't have Makefile notes from years earlier - young guys don't document enough!