feat: add cross-compilation support with --target flag

- Updated build and run commands to accept a --target option for specifying target platforms.
- Enhanced documentation to include cross-compilation usage and supported targets.
- Modified configuration to allow target-specific settings and toolchains.
- Introduced a new test command to run project tests with specified profiles and targets.
- Improved handling of target directories and output structure for different platforms.
- Added support for multiple targets in the configuration file.
- Implemented inheritance for workspace and dependencies based on target and profile.

docs/commands/dcr-test.md

@@ -0,0 +1,44 @@
+# dcr test
+
+Runs the project's test suite.
+
+## Usage
+
+```sh
+dcr test
+dcr test --release
+dcr test --target linux
+dcr test --init
+```
+
+## What `test` does
+
+1. Builds the project with the specified profile/target.
+2. Compiles test files in `tests/` (e.g., `tests/test.c`) into a test binary.
+3. Runs the test binary and parses output for PASS/SKIP/FAIL results.
+4. Reports summary with colored output.
+
+## Test Structure
+
+DCR uses a simple test framework:
+
+- Header: `tests/dcr_test.h` (generated by `dcr test --init`)
+- Test file: `tests/test.c` (template generated by `dcr test --init`)
+- Macros: `TEST(name)`, `TEST_CASE(name)`, `EXPECT(condition)`, `SKIP(reason)`
+- Output: `[PASS] test_name`, `[FAIL] test_name`, or `[SKIP] test_name`
+
+## Config values used
+
+- `package.name`
+- `build.compiler`, `build.language`, `build.standard`
+- `build.cflags`, `build.ldflags`
+- `build.debug` / `build.release`
+- `build.targets` (if specified)
+
+## Notes
+
+- Test binary is linked with the main project (for lib projects) or standalone.
+- `--init` creates `tests/dcr_test.h` and `tests/test.c` if missing.
+- Tests run in release mode by default for performance.
+- Custom test logic can be added by editing `tests/test.c`.
+- Fails if no `tests/test.c` exists (run `dcr test --init` first).