fix: anchor build/ in .gitignore so buildSrc package is tracked

The unanchored `build/` pattern matched the `build/` directory inside
`buildSrc/src/main/kotlin/io/flamingock/build/`, silently dropping
VersionManager.kt and PrintVersionTask.kt from the previous commit and
breaking the CI release build with "Unresolved reference" errors.

Anchoring to `/build/` (matches root only) makes the package visible to
git, and adds the two Kotlin sources that were missing.

Author: dieppa

.gitignore

@@ -1,6 +1,6 @@
 # Gradle
 .gradle/
-build/
+/build/
 !gradle/wrapper/gradle-wrapper.jar
 
 # IDE

buildSrc/src/main/kotlin/io/flamingock/build/PrintVersionTask.kt

@@ -0,0 +1,12 @@
+package io.flamingock.build
+
+import org.gradle.api.DefaultTask
+import org.gradle.api.tasks.TaskAction
+
+abstract class PrintVersionTask : DefaultTask() {
+
+    @TaskAction
+    fun print() {
+        println(project.version)
+    }
+}

buildSrc/src/main/kotlin/io/flamingock/build/VersionManager.kt

@@ -0,0 +1,17 @@
+package io.flamingock.build
+
+object VersionManager {
+
+    private const val SNAPSHOT_SUFFIX = "-SNAPSHOT"
+
+    fun resolveVersion(declaredVersion: String, isRelease: Boolean): String {
+        if (!isRelease) return declaredVersion
+        require(declaredVersion.endsWith(SNAPSHOT_SUFFIX)) {
+            "Cannot release: version '$declaredVersion' does not end with $SNAPSHOT_SUFFIX. " +
+                    "This prevents accidental double-releases."
+        }
+        return declaredVersion.removeSuffix(SNAPSHOT_SUFFIX)
+    }
+
+    fun isSnapshot(version: String): Boolean = version.endsWith(SNAPSHOT_SUFFIX)
+}