Enable caching in container build (#21)

Dockerfile

@@ -1,5 +1,5 @@
 # Build the manager binary
-FROM golang:1.22.2 AS builder
+FROM --platform=$BUILDPLATFORM golang:1.22.2 AS builder
 ARG TARGETOS
 ARG TARGETARCH
 
@@ -23,8 +23,12 @@ COPY bmc/ bmc/
 # was called. For example, if we call make docker-build in a local env which has the Apple Silicon M1 SO
 # the docker BUILDPLATFORM arg will be linux/arm64 when for Apple x86 it will be linux/amd64. Therefore,
 # by leaving it empty we can ensure that the container and binary shipped on it will have the same platform.
-RUN CGO_ENABLED=0 GOOS=${TARGETOS:-linux} GOARCH=${TARGETARCH} go build -a -o manager cmd/manager/main.go
-RUN CGO_ENABLED=0 GOOS=${TARGETOS:-linux} GOARCH=${TARGETARCH} go build -a -o metalprobe cmd/metalprobe/main.go
+RUN --mount=type=cache,target=/root/.cache/go-build \
+    --mount=type=cache,target=/go/pkg \
+    CGO_ENABLED=0 GOOS=${TARGETOS:-linux} GOARCH=${TARGETARCH} go build -a -o manager cmd/manager/main.go
+RUN --mount=type=cache,target=/root/.cache/go-build \
+    --mount=type=cache,target=/go/pkg \
+    CGO_ENABLED=0 GOOS=${TARGETOS:-linux} GOARCH=${TARGETARCH} go build -a -o metalprobe cmd/metalprobe/main.go
 
 
 # Use distroless as minimal base image to package the manager binary