Update swiftly install one-liner and instructions (#936)

* Update the one-liners to explicitly set a swiftly home dir so that the source line works.

Update the swiftly path for macOS based on installer changes

* Add notes about the environment variables and install location customization

* Fix awkward wording in install note.

* Fix awkward wording in macOS install note

* Adjust the one-liners and installation pages for macOS and Linux

Author: cmcgee1024

install/linux/swiftly/index.md

@@ -29,6 +29,8 @@ Run the following command in your terminal, to configure swiftly for your accoun
 ./swiftly init
 ```
 
+Note: You can set the SWIFTLY_HOME_DIR and SWIFTLY_BIN_DIR environment variables to customize your install location.
+
 Your current shell may need some additional steps to update your session. Follow the guidance at the end of the installation for a smooth install experience, such as sourcing the environment file, and rehashing your shell's PATH.
 
 There can be certain packages that need to be installed on your system so that the Swift toolchain can function. The swiftly initialization routine will show you how to install any missing packages.
@@ -64,4 +66,4 @@ Check for updates to swiftly and install them by running the self-update command
 swiftly self-update
 ```
 
-You can discover more about swiftly in the [documentation](https://www.swift.org/swiftly/documentation/swiftlydocs/)
+You can discover more about swiftly in the [documentation](https://www.swift.org/swiftly/documentation/swiftlydocs/)

install/macos/index.md

@@ -15,8 +15,8 @@ title: Install Swift
   <h4>Run this in a terminal:</h4>
   <div class="language-plaintext highlighter-rouge"><div class="highlight"><button>Copy</button><pre class="highlight"><code>curl -O https://download.swift.org/swiftly/darwin/swiftly-{{ site.data.builds.swiftly_release.version }}.pkg &amp;&amp; \
 installer -pkg swiftly-{{ site.data.builds.swiftly_release.version }}.pkg -target CurrentUserHomeDirectory &amp;&amp; \
-~/usr/local/bin/swiftly init --quiet-shell-followup &amp;&amp; \
-. ~/Library/Application\ Support/swiftly/env.sh &amp;&amp; \
+~/.swiftly/bin/swiftly init --quiet-shell-followup &amp;&amp; \
+. ~/.swiftly/env.sh &amp;&amp; \
 hash -r
 </code></pre></div></div>
   <h4>License: <a href="https://raw.githubusercontent.com/swiftlang/swiftly/refs/heads/main/LICENSE.txt">Apache-2.0</a></h4>

install/macos/swiftly/index.md

@@ -14,9 +14,11 @@ installer -pkg swiftly-{{ site.data.builds.swiftly_release.version }}.pkg -targe
 Run the following command in your terminal, to configure swiftly for your account, and automatically download the latest swift toolchain.
 
 ```
-~/usr/local/bin/swiftly init
+~/.swiftly/bin/swiftly init
 ```
 
+Note: You can set the SWIFTLY_HOME_DIR and SWIFTLY_BIN_DIR environment variables to customize the install location.
+
 <div class="warning" markdown="1">
 Your current shell may need some additional steps to update your session. Follow the guidance at the end of the installation for a smooth install experience, such as sourcing the environment file, and rehashing your shell's PATH.
 </div>