Move the stack args to just before they are needed.

This increases layer cacheability so that new stack versions will not
invalide the ghc / cabal install layer.

Author: AlistairB

8.10/buster/Dockerfile

@@ -9,9 +9,6 @@ RUN apt-get update && \
 ARG GHC=8.10.4
 ARG DEBIAN_KEY=427CB69AAC9D00F2A43CAF1CBA3CBA3FFE22B574
 ARG CABAL_INSTALL=3.4
-ARG STACK=2.7.1
-ARG STACK_KEY=C5705533DA4F78D8664B5DC0575159689BEFB442
-ARG STACK_RELEASE_KEY=2C6A674E85EE3FB896AFC9B965101FF31C5C154D
 
 RUN export GNUPGHOME="$(mktemp -d)" && \
     gpg --batch --keyserver keyserver.ubuntu.com --recv-keys ${DEBIAN_KEY} && \
@@ -34,6 +31,10 @@ RUN export GNUPGHOME="$(mktemp -d)" && \
         zlib1g-dev && \
     rm -rf "$GNUPGHOME" /var/lib/apt/lists/*
 
+ARG STACK=2.7.1
+ARG STACK_KEY=C5705533DA4F78D8664B5DC0575159689BEFB442
+ARG STACK_RELEASE_KEY=2C6A674E85EE3FB896AFC9B965101FF31C5C154D
+
 RUN export GNUPGHOME="$(mktemp -d)" && \
     gpg --batch --keyserver ha.pool.sks-keyservers.net --recv-keys ${STACK_KEY} && \
     gpg --batch --keyserver ha.pool.sks-keyservers.net --recv-keys ${STACK_RELEASE_KEY} && \

8.10/stretch/Dockerfile

@@ -9,9 +9,6 @@ RUN apt-get update && \
 ARG GHC=8.10.4
 ARG DEBIAN_KEY=427CB69AAC9D00F2A43CAF1CBA3CBA3FFE22B574
 ARG CABAL_INSTALL=3.4
-ARG STACK=2.7.1
-ARG STACK_KEY=C5705533DA4F78D8664B5DC0575159689BEFB442
-ARG STACK_RELEASE_KEY=2C6A674E85EE3FB896AFC9B965101FF31C5C154D
 
 RUN export GNUPGHOME="$(mktemp -d)" && \
     gpg --batch --keyserver keyserver.ubuntu.com --recv-keys ${DEBIAN_KEY} && \
@@ -34,6 +31,10 @@ RUN export GNUPGHOME="$(mktemp -d)" && \
         zlib1g-dev && \
     rm -rf "$GNUPGHOME" /var/lib/apt/lists/*
 
+ARG STACK=2.7.1
+ARG STACK_KEY=C5705533DA4F78D8664B5DC0575159689BEFB442
+ARG STACK_RELEASE_KEY=2C6A674E85EE3FB896AFC9B965101FF31C5C154D
+
 RUN export GNUPGHOME="$(mktemp -d)" && \
     gpg --batch --keyserver ha.pool.sks-keyservers.net --recv-keys ${STACK_KEY} && \
     gpg --batch --keyserver ha.pool.sks-keyservers.net --recv-keys ${STACK_RELEASE_KEY} && \

9.0/buster/Dockerfile

@@ -9,9 +9,6 @@ RUN apt-get update && \
 ARG GHC=9.0.1
 ARG DEBIAN_KEY=427CB69AAC9D00F2A43CAF1CBA3CBA3FFE22B574
 ARG CABAL_INSTALL=3.4
-ARG STACK=2.7.1
-ARG STACK_KEY=C5705533DA4F78D8664B5DC0575159689BEFB442
-ARG STACK_RELEASE_KEY=2C6A674E85EE3FB896AFC9B965101FF31C5C154D
 
 RUN export GNUPGHOME="$(mktemp -d)" && \
     gpg --batch --keyserver keyserver.ubuntu.com --recv-keys ${DEBIAN_KEY} && \
@@ -34,6 +31,10 @@ RUN export GNUPGHOME="$(mktemp -d)" && \
         zlib1g-dev && \
     rm -rf "$GNUPGHOME" /var/lib/apt/lists/*
 
+ARG STACK=2.7.1
+ARG STACK_KEY=C5705533DA4F78D8664B5DC0575159689BEFB442
+ARG STACK_RELEASE_KEY=2C6A674E85EE3FB896AFC9B965101FF31C5C154D
+
 RUN export GNUPGHOME="$(mktemp -d)" && \
     gpg --batch --keyserver ha.pool.sks-keyservers.net --recv-keys ${STACK_KEY} && \
     gpg --batch --keyserver ha.pool.sks-keyservers.net --recv-keys ${STACK_RELEASE_KEY} && \

9.0/stretch/Dockerfile

@@ -9,9 +9,6 @@ RUN apt-get update && \
 ARG GHC=9.0.1
 ARG DEBIAN_KEY=427CB69AAC9D00F2A43CAF1CBA3CBA3FFE22B574
 ARG CABAL_INSTALL=3.4
-ARG STACK=2.7.1
-ARG STACK_KEY=C5705533DA4F78D8664B5DC0575159689BEFB442
-ARG STACK_RELEASE_KEY=2C6A674E85EE3FB896AFC9B965101FF31C5C154D
 
 RUN export GNUPGHOME="$(mktemp -d)" && \
     gpg --batch --keyserver keyserver.ubuntu.com --recv-keys ${DEBIAN_KEY} && \
@@ -34,6 +31,10 @@ RUN export GNUPGHOME="$(mktemp -d)" && \
         zlib1g-dev && \
     rm -rf "$GNUPGHOME" /var/lib/apt/lists/*
 
+ARG STACK=2.7.1
+ARG STACK_KEY=C5705533DA4F78D8664B5DC0575159689BEFB442
+ARG STACK_RELEASE_KEY=2C6A674E85EE3FB896AFC9B965101FF31C5C154D
+
 RUN export GNUPGHOME="$(mktemp -d)" && \
     gpg --batch --keyserver ha.pool.sks-keyservers.net --recv-keys ${STACK_KEY} && \
     gpg --batch --keyserver ha.pool.sks-keyservers.net --recv-keys ${STACK_RELEASE_KEY} && \