Combine the 2 Dockerfiles and add ROCm

This renames Dockerfile.build to Dockerfile, and adds some new stages
to support 2 modes of building - the build_linux.sh script uses
intermediate stages to extract the artifacts for ./dist, and the default
build generates a container image usable by both cuda and rocm cards.
This required transitioniing the x86 base to the rocm image to avoid
layer bloat.

scripts/build_linux.sh

@@ -9,7 +9,15 @@ BUILD_ARCH=${BUILD_ARCH:-"amd64 arm64"}
 mkdir -p dist
 
 for TARGETARCH in ${BUILD_ARCH}; do
-    docker build --platform=linux/$TARGETARCH --build-arg=GOFLAGS --build-arg=CGO_CFLAGS --build-arg=OLLAMA_CUSTOM_CPU_DEFS -f Dockerfile.build -t builder:$TARGETARCH .
+    docker build \
+        --platform=linux/$TARGETARCH \
+        --build-arg=GOFLAGS \
+        --build-arg=CGO_CFLAGS \
+        --build-arg=OLLAMA_CUSTOM_CPU_DEFS \
+        --target build-$TARGETARCH \
+        -f Dockerfile \
+        -t builder:$TARGETARCH \
+        .
     docker create --platform linux/$TARGETARCH --name builder-$TARGETARCH builder:$TARGETARCH
     docker cp builder-$TARGETARCH:/go/src/github.com/jmorganca/ollama/ollama ./dist/ollama-linux-$TARGETARCH
     docker rm builder-$TARGETARCH