build: make a macOS ARM64 build to support Apple Silicon - Fixes #4786

- add `-macos-sdk` and `-macos-arch` to adjust CGO_CFLAGS and CGO_LDFLAGS
    - select macOS SDK 11.1 and arch arm64 when building
- add -cgo-cflags and -cgo-ldflags to set CGO_CFLAGS and CGO_LDFLAGS
    - add back /usr/local to pickup fuse headers and library
- add `-env` to cross-compile
- add macOS/arm64 to download matrix

.github/workflows/build.yml

@@ -19,7 +19,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        job_name: ['linux', 'mac', 'windows_amd64', 'windows_386', 'other_os', 'go1.13', 'go1.14', 'go1.15']
+        job_name: ['linux', 'mac_amd64', 'mac_arm64', 'windows_amd64', 'windows_386', 'other_os', 'go1.13', 'go1.14', 'go1.15']
 
         include:
           - job_name: linux
@@ -32,7 +32,7 @@ jobs:
             racequicktest: true
             deploy: true
 
-          - job_name: mac
+          - job_name: mac_amd64
             os: macOS-latest
             go: '1.16.0-rc1'
             gotags: 'cmount'
@@ -41,6 +41,13 @@ jobs:
             racequicktest: true
             deploy: true
 
+          - job_name: mac_arm64
+            os: macOS-latest
+            go: '1.16.0-rc1'
+            gotags: 'cmount'
+            build_flags: '-include "^darwin/arm64" -cgo -macos-arch arm64 -macos-sdk macosx11.1 -cgo-cflags=-I/usr/local/include -cgo-ldflags=-L/usr/local/lib'
+            deploy: true
+
           - job_name: windows_amd64
             os: windows-latest
             go: '1.16.0-rc1'
@@ -65,7 +72,7 @@ jobs:
           - job_name: other_os
             os: ubuntu-latest
             go: '1.16.0-rc1'
-            build_flags: '-exclude "^(windows/|darwin/amd64|linux/)"'
+            build_flags: '-exclude "^(windows/|darwin/|linux/)"'
             compile_all: true
             deploy: true