[installer] Do not follow an existing symbolic link when overwriting

kateinoigakukun · Anka · commit 64b3934ad9bd · 2024-05-29T01:17:59.000Z
Without `-h` option, `ln` command makes a symbolic link under the existing
link destination like `Toolchains/swift-DEVELOPMENT-SNAPSHOT-XX.xctoolchain/`.

```
$ ln -fs swift-DEVELOPMENT-SNAPSHOT-XX.xctoolchain swift-latest.xctoolchain
$ ln -fs swift-DEVELOPMENT-SNAPSHOT-YY.xctoolchain swift-latest.xctoolchain
$ tree
|-- swift-DEVELOPMENT-SNAPSHOT-XX.xctoolchain
|   |-- swift-DEVELOPMENT-SNAPSHOT-YY.xctoolchain -&gt; swift-DEVELOPMENT-SNAPSHOT-YY.xctoolchain
|-- swift-DEVELOPMENT-SNAPSHOT-YY.xctoolchain
|-- swift-latest.xctoolchain -&gt; swift-DEVELOPMENT-SNAPSHOT-XX.xctoolchain
```

So we should not follow the existing symbolic link even if it already
exists.
diff --git a/utils/darwin-installer-scripts/postinstall b/utils/darwin-installer-scripts/postinstall
@@ -13,4 +13,4 @@
 
 INSTALLED_TOOLCHAIN=$2
 
-ln -fs "${INSTALLED_TOOLCHAIN}" "${INSTALLED_TOOLCHAIN%/*}/swift-latest.xctoolchain"
+ln -fhs "${INSTALLED_TOOLCHAIN}" "${INSTALLED_TOOLCHAIN%/*}/swift-latest.xctoolchain"

Original file line number	Diff line number	Diff line change
`@@ -13,4 +13,4 @@`
`13`	`13`
`14`	`14`	`INSTALLED_TOOLCHAIN=$2`
`15`	`15`
`16`		`-ln -fs "${INSTALLED_TOOLCHAIN}" "${INSTALLED_TOOLCHAIN%/*}/swift-latest.xctoolchain"`
	`16`	`+ln -fhs "${INSTALLED_TOOLCHAIN}" "${INSTALLED_TOOLCHAIN%/*}/swift-latest.xctoolchain"`