fix: lake: set MACOSX_DEPLOYMENT_TARGET for shared libs (#6631)

This PR sets `MACOSX_DEPLOYMENT_TARGET` for shared libraries (it was
previously only set for executables).

(cherry picked from commit 749a82a)

src/lake/Lake/Build/Actions.lean

@@ -88,6 +88,17 @@ def compileStaticLib
     args := #["rcs", libFile.toString] ++ oFiles.map toString
   }
 
+private def getMacOSXDeploymentEnv : BaseIO (Array (String × Option String)) := do
+  -- It is difficult to identify the correct minor version here, leading to linking warnings like:
+  -- `ld64.lld: warning: /usr/lib/system/libsystem_kernel.dylib has version 13.5.0, which is newer than target minimum of 13.0.0`
+  -- In order to suppress these we set the MACOSX_DEPLOYMENT_TARGET variable into the far future.
+  if System.Platform.isOSX then
+    match (← IO.getEnv "MACOSX_DEPLOYMENT_TARGET") with
+    | some _ => return #[]
+    | none => return #[("MACOSX_DEPLOYMENT_TARGET", some "99.0")]
+  else
+    return #[]
+
 def compileSharedLib
   (libFile : FilePath) (linkArgs : Array String)
   (linker : FilePath := "cc")
@@ -96,6 +107,7 @@ def compileSharedLib
   proc {
     cmd := linker.toString
     args := #["-shared", "-o", libFile.toString] ++ linkArgs
+    env := ← getMacOSXDeploymentEnv
   }
 
 def compileExe
@@ -106,16 +118,7 @@ def compileExe
   proc {
     cmd := linker.toString
     args := #["-o", binFile.toString] ++ linkFiles.map toString ++ linkArgs
-    env := ← do
-      -- It is difficult to identify the correct minor version here, leading to linking warnings like:
-      -- `ld64.lld: warning: /usr/lib/system/libsystem_kernel.dylib has version 13.5.0, which is newer than target minimum of 13.0.0`
-      -- In order to suppress these we set the MACOSX_DEPLOYMENT_TARGET variable into the far future.
-      if System.Platform.isOSX then
-        match (← IO.getEnv "MACOSX_DEPLOYMENT_TARGET") with
-        | some _ => pure #[]
-        | none => pure #[("MACOSX_DEPLOYMENT_TARGET", some "99.0")]
-      else
-        pure #[]
+    env := ← getMacOSXDeploymentEnv
   }
 
 /-- Download a file using `curl`, clobbering any existing file. -/