Introduce GOAMD64 variable with default=v2 for AMD64 arch. (#12371)

See #11715

Makefile

@@ -1,4 +1,5 @@
 GO ?= go # if using docker, should not need to be installed/linked
+GOAMD64_VERSION ?= v2 # See https://go.dev/wiki/MinimumRequirements#microarchitecture-support
 GOBINREL = build/bin
 GOBIN = $(CURDIR)/$(GOBINREL)
 UNAME = $(shell uname) # Supported: Darwin, Linux
@@ -32,6 +33,10 @@ ifeq ($(shell uname -m), aarch64)
 	CGO_CFLAGS += -D__BLST_PORTABLE__
 endif
 
+# Configure GOAMD64 env.variable for AMD64 architecture:
+ifeq ($(shell uname -m),x86_64)
+	CPU_ARCH= GOAMD64=${GOAMD64_VERSION}
+endif
 
 CGO_CFLAGS += -Wno-unknown-warning-option -Wno-enum-int-mismatch -Wno-strict-prototypes -Wno-unused-but-set-variable -O3
 
@@ -58,9 +63,9 @@ PACKAGE = github.com/erigontech/erigon
 GO_FLAGS += -trimpath -tags $(BUILD_TAGS) -buildvcs=false 
 GO_FLAGS += -ldflags "-X ${PACKAGE}/params.GitCommit=${GIT_COMMIT} -X ${PACKAGE}/params.GitBranch=${GIT_BRANCH} -X ${PACKAGE}/params.GitTag=${GIT_TAG}"
 
-GOBUILD = CGO_CFLAGS="$(CGO_CFLAGS)" CGO_LDFLAGS="$(CGO_LDFLAGS)" GOPRIVATE="$(GOPRIVATE)" $(GO) build $(GO_FLAGS)
-GO_DBG_BUILD = CGO_CFLAGS="$(CGO_CFLAGS) -DMDBX_DEBUG=1" CGO_LDFLAGS="$(CGO_LDFLAGS)" GOPRIVATE="$(GOPRIVATE)" $(GO) build -tags $(BUILD_TAGS),debug -gcflags=all="-N -l"  # see delve docs
-GOTEST = CGO_CFLAGS="$(CGO_CFLAGS)" CGO_LDFLAGS="$(CGO_LDFLAGS)" GOPRIVATE="$(GOPRIVATE)" GODEBUG=cgocheck=0 GOTRACEBACK=1 $(GO) test $(GO_FLAGS) ./... -p 2
+GOBUILD = ${CPU_ARCH} CGO_CFLAGS="$(CGO_CFLAGS)" CGO_LDFLAGS="$(CGO_LDFLAGS)" GOPRIVATE="$(GOPRIVATE)" $(GO) build $(GO_FLAGS)
+GO_DBG_BUILD = ${CPU_ARCH} CGO_CFLAGS="$(CGO_CFLAGS) -DMDBX_DEBUG=1" CGO_LDFLAGS="$(CGO_LDFLAGS)" GOPRIVATE="$(GOPRIVATE)" $(GO) build -tags $(BUILD_TAGS),debug -gcflags=all="-N -l"  # see delve docs
+GOTEST = ${CPU_ARCH} CGO_CFLAGS="$(CGO_CFLAGS)" CGO_LDFLAGS="$(CGO_LDFLAGS)" GOPRIVATE="$(GOPRIVATE)" GODEBUG=cgocheck=0 GOTRACEBACK=1 $(GO) test $(GO_FLAGS) ./... -p 2
 
 default: all