support runner.arch (#1290)

* support runner.arch

Signed-off-by: Fabian Kammel <fk@edgeless.systems>

* add arch to runner definition

Signed-off-by: Fabian Kammel <fk@edgeless.systems>

* get architecture from docker

Signed-off-by: Fabian Kammel <fk@edgeless.systems>

* Update pkg/container/docker_run.go

Co-authored-by: ChristopherHX <christopher.homberger@web.de>

* lint: goimport file

Signed-off-by: Fabian Kammel <fk@edgeless.systems>
Co-authored-by: Casey Lee <caseypl@amazon.com>
Co-authored-by: ChristopherHX <christopher.homberger@web.de>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

pkg/runner/expression.go

@@ -7,6 +7,7 @@ import (
 	"strings"
 
 	"github.com/nektos/act/pkg/common"
+	"github.com/nektos/act/pkg/container"
 	"github.com/nektos/act/pkg/exprparser"
 	"gopkg.in/yaml.v3"
 )
@@ -47,6 +48,7 @@ func (rc *RunContext) NewExpressionEvaluator(ctx context.Context) ExpressionEval
 		Steps: rc.getStepsContext(),
 		Runner: map[string]interface{}{
 			"os":         "Linux",
+			"arch":       container.RunnerArch(ctx),
 			"temp":       "/tmp",
 			"tool_cache": "/opt/hostedtoolcache",
 		},
@@ -92,6 +94,7 @@ func (rc *RunContext) NewStepExpressionEvaluator(ctx context.Context, step step)
 		Steps:  rc.getStepsContext(),
 		Runner: map[string]interface{}{
 			"os":         "Linux",
+			"arch":       container.RunnerArch(ctx),
 			"temp":       "/tmp",
 			"tool_cache": "/opt/hostedtoolcache",
 		},