Look for the skiko library in the libs directory of the JVM. (#328)

In some packagings, Skiko (+its data file) will be placed alongside
the other shared libraries used by the JVM. This has some advantages
with respect to code signing, and also avoids a .skiko directory
littering the user's home directory. That's especially important on
Windows where dotfiles/dotdirs don't work.

The system property still overrides this.
Co-authored-by: Mike Hearn <mike@hydraulic.software>

skiko/src/jvmMain/kotlin/org/jetbrains/skiko/Library.kt

 package org.jetbrains.skiko
 
 import org.jetbrains.skia.Bitmap
-import java.io.BufferedReader
 import java.io.File
-import java.io.InputStreamReader
 import java.nio.file.Files
 import java.nio.file.StandardCopyOption
 import java.util.concurrent.atomic.AtomicBoolean
@@ -52,52 +50,72 @@ object Library {
     // This function does the following: on request to load given resource,
     // it checks if resource with given name is found in content-derived directory
     // in Skiko's home, and if not - unpacks it. Also, it could load additional
-    // localization resource on platforms wher it is needed.
+    // localization resource on platforms where it is needed.
     @Synchronized
     fun load() {
         if (loaded.compareAndExchange(false, true)) return
+
+        // Find/unpack a usable copy of the native library.
+        findAndLoad()
+
+        // TODO move properties to SkikoProperties
+        Setup.init()
+
+        try {
+            // Init code executed after library was loaded.
+            org.jetbrains.skia.impl.Library._nAfterLoad()
+        } catch (t: Throwable) {
+            t.printStackTrace()
+        }
+    }
+
+    private fun findAndLoad() {
         val name = "skiko-$hostId"
         val platformName = System.mapLibraryName(name)
         val icu = if (hostOs.isWindows) "icudtl.dat" else null
 
+        // First try: system property is set.
         if (skikoLibraryPath != null) {
             val library = File(File(skikoLibraryPath), platformName)
             loadLibraryOrCopy(library)
-            if (icu != null && copyDir != null) {
+            if (icu != null && copyDir != null)
                 unpackIfNeeded(copyDir!!, icu, true)
+            return
         }
-        } else {
+
+        // Second try: load it from the bin/ or lib/ directory relative to the JVM home.
+        // The user might have placed the native files alongside the other JVM libraries
+        // for signing purposes, so we'll find it here if so.
+        val jvmFiles = File(System.getProperty("java.home"), if (hostOs.isWindows) "bin" else "lib")
+        val pathInJvm = jvmFiles.resolve(platformName)
+        if (pathInJvm.exists() && icu?.let { (jvmFiles.resolve(it)).exists() } != false) {
+            loadLibraryOrCopy(pathInJvm)
+            return
+        }
+
+        // Third try: look up in or extract to a local cache directory.
+        // Key the cache by the hash of the library.
         val hashResourceStream = Library::class.java.getResourceAsStream(
             "/$platformName.sha256"
         ) ?: throw LibraryLoadException(
             "Cannot find $platformName.sha256, proper native dependency missing."
         )
-            val hash = hashResourceStream.use {
-                BufferedReader(InputStreamReader(it)).lines().toArray()[0] as String
-            }
+        val hash = hashResourceStream.use { it.bufferedReader().readLine() }
+
         val cacheDir = File(File(cacheRoot), hash)
         cacheDir.mkdirs()
         val library = unpackIfNeeded(cacheDir, platformName, false)
         loadLibraryOrCopy(library)
         if (icu != null) {
             if (copyDir != null) {
+                // We made a duplicate to resolve classloader conflicts.
                 unpackIfNeeded(copyDir!!, icu, true)
             } else {
+                // Normal path where Skiko is loaded only once.
                 unpackIfNeeded(cacheDir, icu, false)
             }
         }
     }
-
-        // TODO move properties to SkikoProperties
-        Setup.init()
-
-        try {
-            // Init code executed after library was loaded.
-            org.jetbrains.skia.impl.Library._nAfterLoad()
-        } catch (t: Throwable) {
-            t.printStackTrace()
-        }
-    }
 }
 
 // We have to keep this tiny class in Skiko for testing purposes.