feat: Implement build state tracking and interactive package specification creation

- Added StateTracker to manage build steps and allow resuming interrupted builds.
- Updated post_extract function to utilize StateTracker for patch and command execution.
- Introduced makefile.rs to handle building and installing packages via Makefile.
- Created interactive.rs for an interactive package specification creator with SHA256 computation for source URLs.
- Enhanced checksum verification to support multiple algorithms (SHA256, SHA512, MD5).
- Added example configuration files in contrib for system-wide and user-level Depot configurations.
- Updated tests to cover new functionality and ensure correctness of state tracking and interactive creation.

contrib/depot.d/build.toml

@@ -0,0 +1,17 @@
+[flags]
+# Default build flags applied to all packages via /etc/depot.d/build.toml
+# Compiler selection
+cc = "gcc"
+
+# Default CFLAGS
+cflags = ["-O2"]
+cflags += ["-pipe"]
+
+# Default LDFLAGS
+ldflags = ["-Wl,-O1"]
+
+# CARCH short name (can be overridden per-package)
+carch = "x86_64"
+
+# Example of appending per-package cflags: (will be exposed as build.cflags appends)
+# cflags += ["-march=native"]