Fixed build error on macOS dist

The error was due to an increased git security constraints

  ...
  go: downloading github.com/xanzy/ssh-agent v0.2.1
  go: downloading gopkg.in/warnings.v0 v0.1.2
  error obtaining VCS status: exit status 128
	Use -buildvcs=false to disable VCS stamping.
  Error: failed building for darwin/amd64: exit status 1
  failed building for darwin/amd64: exit status 1
  task: Failed to run task "dist:macOS_64bit": exit status 1

To fix this I followed the suggestion here elastic/golang-crossbuild#232

Author: cmaglie

Diff for: DistTasks.yml

@@ -201,11 +201,12 @@ tasks:
     desc: Builds Mac OS X 64 bit binaries
     dir: "{{.DIST_DIR}}"
     cmds:
+      # "git config safe.directory" is required until this is fixed https://github.com/elastic/golang-crossbuild/issues/232
       - |
         docker run -v `pwd`/..:/home/build -w /home/build \
         -e CGO_ENABLED=1 \
         {{.CONTAINER}}:{{.CONTAINER_TAG}} \
-        --build-cmd "{{.BUILD_COMMAND}}" \
+        --build-cmd "git config --global --add safe.directory /home/build && {{.BUILD_COMMAND}}" \
         -p "{{.BUILD_PLATFORM}}"
 
         tar cz -C {{.PLATFORM_DIR}} {{.PROJECT_NAME}} -C ../.. LICENSE.txt  -f {{.PACKAGE_NAME}}
@@ -235,11 +236,12 @@ tasks:
     desc: Builds Mac OS X ARM64 binaries
     dir: "{{.DIST_DIR}}"
     cmds:
+      # "git config safe.directory" is required until this is fixed https://github.com/elastic/golang-crossbuild/issues/232
       - |
         docker run -v `pwd`/..:/home/build -w /home/build \
         -e CGO_ENABLED=1 \
         {{.CONTAINER}}:{{.CONTAINER_TAG}} \
-        --build-cmd "{{.BUILD_COMMAND}}" \
+        --build-cmd "git config --global --add safe.directory /home/build && {{.BUILD_COMMAND}}" \
         -p "{{.BUILD_PLATFORM}}"
 
         tar cz -C {{.PLATFORM_DIR}} {{.PROJECT_NAME}} -C ../.. LICENSE.txt  -f {{.PACKAGE_NAME}}