feat: update user configuration example and add development package support

- Enhanced the user.depot.toml.example file with additional comments and options for user-local preferences.
- Bumped version from 0.35.0 to 0.35.1 in meson.build.
- Introduced a new option for DEPOT_DEVELOPMENT_PACKAGE in meson_options.txt.
- Added functions to handle the requested development package in build_options.rs.
- Updated various builder files (autotools.rs, cmake.rs, custom.rs, meson.rs, perl.rs) to support passing build flags.
- Implemented checks for the required development package during source builds in commands.rs and commands/build_cmd.rs.
- Added tests to ensure the correct behavior of development package requirements and source build warnings.
- Modified manual source handling in source/mod.rs to validate local manual sources before proceeding with builds.
- Updated cargo build and test scripts to accept a new development package argument.
- Added VSCode settings to disable automatic configuration on open.

contrib/user.depot.toml.example

@@ -1,18 +1,35 @@
 # Example per-user configuration (~/.config/depot.toml)
+#
+# Use this file for local preferences that should not affect other users on the
+# same machine. System-wide defaults still come from /etc/depot.toml and
+# /etc/depot.d/*.toml unless you override them here.
 
 [build]
+# A user-local prefix is useful when you are building software for your own
+# account instead of assembling system packages.
 prefix = "/usr/local"
+
+# Personal toolchain preference.
 cc = "clang"
+# cxx = "clang++"
 
 [build.flags]
+# User-local compiler preferences.
 cflags = ["-O2"]
 cflags += ["-g"]
 carch = "x86_64"
 
-[install]
-test_deps = false
+# Examples:
+# cxxflags = ["-O2", "-g"]
+# ldflags = ["-Wl,-O1"]
+# makeflags = "-j4"
 
-# Optional install directory overrides for supported builders
-#bindir = "/usr/local/bin"
-#sbindir = "/usr/local/sbin"
-#libdir = "/usr/local/lib"
+# Optional install directory overrides for supported builders.
+# bindir = "/usr/local/bin"
+# sbindir = "/usr/local/sbin"
+# libdir = "/usr/local/lib"
+# datadir = "/usr/local/share"
+
+[install]
+# Install test dependencies automatically for your own source builds.
+test_deps = false