Specify in Gradle the minimum supported Java version (#30)

Author: piotrrzysko

build.gradle

@@ -29,8 +29,13 @@ repositories {
 }
 
 java {
-    toolchain {
-        languageVersion = JavaLanguageVersion.of(18)
+    // It seems that specifying the minimum supported Java version while allowing the use of newer
+    // ones isn't possible in Gradle. To test the library against multiple Java versions, the
+    // workaround proposed in https://github.com/gradle/gradle/issues/16256 has been applied:
+    if (!JavaVersion.current().isCompatibleWith(JavaVersion.VERSION_18)) {
+        toolchain {
+            languageVersion = JavaLanguageVersion.of(18)
+        }
     }
     withJavadocJar()
     withSourcesJar()

settings.gradle

@@ -1,5 +1 @@
-plugins {
-    id("org.gradle.toolchains.foojay-resolver-convention") version "0.7.0"
-}
-
 rootProject.name = 'simdjson-java'