Work around swiftly install behaviors (#85)

* Install swiftly to home folder to avoid caching-related issues

* Avoid initial toolchain installation and errors on manual install

In the current version, `swiftly install --use` exits with non-zero if it decides that there are post-install commands to execute (falsely, even). Telling it to write its worries to a local files avoids this and lets the build proceed.

Author: vzsg

bin/compile

@@ -7,7 +7,6 @@
 set -e
 set -o pipefail
 
-
 BIN_DIR=$(
   cd $(dirname $0)
   pwd
@@ -35,7 +34,6 @@ SWIFT_VERSION="latest"
 SWIFT_BUILD_CONFIGURATION="release"
 SWIFT_BUILD_FLAGS=""
 
-
 if [ -f "$BUILD_DIR/.swift-version" ]; then
   SWIFT_VERSION=$(cat "$BUILD_DIR/.swift-version" | tr -d '[[:space:]]')
   puts-step "Using Swift $SWIFT_VERSION (from package .swift-version file)"
@@ -64,7 +62,7 @@ else
   SWIFT_BACKTRACE_EXECUTABLE="swift-backtrace-static"
 fi
 
-mkdir -p "$CACHE_DIR/$STACK"
+mkdir -p "$CACHE_DIR"
 source "$BIN_DIR/steps/swiftly"
 
 cd "$BUILD_DIR"

bin/steps/swiftly

@@ -1,19 +1,10 @@
-export SWIFTLY_HOME_DIR="$CACHE_DIR/$STACK/share/swiftly"
-export SWIFTLY_BIN_DIR="$CACHE_DIR/$STACK/bin"
-export PATH="$SWIFTLY_BIN_DIR:$PATH"
+puts-step Installing swiftly...
 
-if [ -d "$SWIFTLY_HOME_DIR" ]; then
-  puts-step "Swiftly already installed, updating..."
-  swiftly self-update
-else
-  puts-step Installing swiftly...
-
-  curl -O https://download.swift.org/swiftly/linux/swiftly-$(uname -m).tar.gz && \
-    tar zxf swiftly-$(uname -m).tar.gz && \
-    ./swiftly init --quiet-shell-followup && \
-    . ~/.local/share/swiftly/env.sh && \
-    hash -r
-fi
+curl -O https://download.swift.org/swiftly/linux/swiftly-$(uname -m).tar.gz && \
+  tar zxf swiftly-$(uname -m).tar.gz && \
+  ./swiftly init --quiet-shell-followup --skip-install -y && \
+  . ~/.local/share/swiftly/env.sh && \
+  hash -r
 
 puts-step Installing Swift...
-swiftly install --use $SWIFT_VERSION
+swiftly install --use $SWIFT_VERSION --post-install-file __fake_post_install.sh --verbose