Only use ghcup where needed

.gitlab/ci.sh

@@ -4,49 +4,26 @@ set -Eeuo pipefail
 
 source "$CI_PROJECT_DIR/.gitlab/common.sh"
 
-export GHCUP_INSTALL_BASE_PREFIX="$CI_PROJECT_DIR/toolchain"
+if [[ "$(uname)" == "Linux" ]]; then
+    export PATH="/opt/ghc/${GHC_VERSION}/bin:${PATH}"
+# Not all runners use ci-images, so ghcup is used.
+else
+    . "$CI_PROJECT_DIR/.gitlab/ghcup.sh"
+fi
+
 export CABAL_DIR="$CI_PROJECT_DIR/cabal"
 
 case "$(uname)" in
     MSYS_*|MINGW*)
         export CABAL_DIR="$(cygpath -w "$CABAL_DIR")"
-        GHCUP_BINDIR="${GHCUP_INSTALL_BASE_PREFIX}/ghcup/bin"
         EXE_EXT=".exe"
         ;;
     *)
-        GHCUP_BINDIR="${GHCUP_INSTALL_BASE_PREFIX}/.ghcup/bin"
         EXE_EXT=""
         ;;
 esac
 
 mkdir -p "$CABAL_DIR"
-mkdir -p "$GHCUP_BINDIR"
-export PATH="$GHCUP_BINDIR:$PATH"
-
-export BOOTSTRAP_HASKELL_NONINTERACTIVE=1
-export BOOTSTRAP_HASKELL_GHC_VERSION=$GHC_VERSION
-export BOOTSTRAP_HASKELL_CABAL_VERSION=$CABAL_INSTALL_VERSION
-export BOOTSTRAP_HASKELL_ADJUST_CABAL_CONFIG=yes
-# We don't use stack, and it isn't available on i386-deb9
-export BOOTSTRAP_HASKELL_INSTALL_NO_STACK=yes
-
-# for some reason the subshell doesn't pick up the arm64 environment on darwin
-# and starts installing x86_64 GHC
-case "$(uname -s)" in
-    "Darwin"|"darwin")
-        case "$(/usr/bin/arch)" in
-            aarch64|arm64|armv8l)
-                curl --proto '=https' --tlsv1.2 -sSf https://get-ghcup.haskell.org | arch -arm64 /bin/bash
-                ;;
-            *)
-                curl --proto '=https' --tlsv1.2 -sSf https://get-ghcup.haskell.org | sh
-                ;;
-        esac
-        ;;
-    *)
-        curl --proto '=https' --tlsv1.2 -sSf https://get-ghcup.haskell.org | sh
-        ;;
-esac
 
 # https://github.com/haskell/cabal/issues/7313#issuecomment-811851884
 # and
@@ -74,7 +51,6 @@ case "$(uname)" in
 esac
 
 args=(
-    -w "ghc-$GHC_VERSION"
     --disable-profiling
     --enable-executable-stripping
     --project-file=cabal.project.release

.gitlab/ghcup.sh

@@ -0,0 +1,38 @@
+export GHCUP_INSTALL_BASE_PREFIX="$CI_PROJECT_DIR/toolchain"
+
+case "$(uname)" in
+    MSYS_*|MINGW*)
+        GHCUP_BINDIR="${GHCUP_INSTALL_BASE_PREFIX}/ghcup/bin"
+        ;;
+    *)
+        GHCUP_BINDIR="${GHCUP_INSTALL_BASE_PREFIX}/.ghcup/bin"
+        ;;
+esac
+
+mkdir -p "$GHCUP_BINDIR"
+export PATH="$GHCUP_BINDIR:$PATH"
+
+export BOOTSTRAP_HASKELL_NONINTERACTIVE=1
+export BOOTSTRAP_HASKELL_GHC_VERSION=$GHC_VERSION
+export BOOTSTRAP_HASKELL_CABAL_VERSION=$CABAL_INSTALL_VERSION
+export BOOTSTRAP_HASKELL_ADJUST_CABAL_CONFIG=yes
+# We don't use stack, and it isn't available on i386-deb9
+export BOOTSTRAP_HASKELL_INSTALL_NO_STACK=yes
+
+# for some reason the subshell doesn't pick up the arm64 environment on darwin
+# and starts installing x86_64 GHC
+case "$(uname -s)" in
+    "Darwin"|"darwin")
+        case "$(/usr/bin/arch)" in
+            aarch64|arm64|armv8l)
+                curl --proto '=https' --tlsv1.2 -sSf https://get-ghcup.haskell.org | arch -arm64 /bin/bash
+                ;;
+            *)
+                curl --proto '=https' --tlsv1.2 -sSf https://get-ghcup.haskell.org | sh
+                ;;
+        esac
+        ;;
+    *)
+        curl --proto '=https' --tlsv1.2 -sSf https://get-ghcup.haskell.org | sh
+        ;;
+esac