feat(build): add freestanding, lto, strip, panic-abort, and codegen-units support in dcr.toml

docs/reference/build-profiles.mdx

@@ -37,6 +37,23 @@ Set `inherit = false` to disable array inheritance (only profile's own arrays ar
 | `debug` | `-O0 -g -Wall -Wextra -fno-omit-frame-pointer -DDCR_DEBUG` |
 | `release` | `-O3 -DNDEBUG` |
 
+These defaults are composed from the `opt_level`, `debug`, and `warnings` fields and can
+be overridden per-profile:
+
+```toml
+[build.release]
+opt_level = "z"
+lto = true
+strip = true
+panic = "abort"
+codegen-units = "1"
+
+[build.debug]
+opt_level = "1"
+debug = false
+warnings = ["all", "error"]
+```
+
 ## Target-specific profiles
 
 ```toml

docs/reference/build-system.mdx

@@ -20,6 +20,10 @@ DCR supports 4 compilation backends. Selection is automatic based on file extens
 - Compiler resolved via `resolve_compiler()`: `DCR_COMPILER` > `DCR_CC` > `[toolchain]` > `build.compiler` > `PATH`
 - Supports `.d` files for header dependency tracking
 - Flags: `-std=`, `-MMD -MF`, `-c -o`, `-I`, `-L`, `-l`
+- Conditional flags based on config:
+  - `freestanding` or bare-metal target: `-ffreestanding` (compile), `-nostdlib -static` (link)
+  - `lto`: `-flto` (compile + link)
+  - `panic = "abort"`: `-fno-exceptions` (C++ only), `-fno-unwind-tables`, `-fno-asynchronous-unwind-tables`
 
 ### MSVC
 

docs/reference/cross-compilation.mdx

@@ -37,9 +37,19 @@ target = "aarch64-unknown-linux-gnu"
 # Auto: cflags += ["--target=aarch64-unknown-linux-gnu"]
 ```
 
-## Bare-Metal
+## Bare-Metal / Freestanding
 
-For targets containing `none`, `-elf`, `eabi`, or `baremetal`, DCR default flags are disabled (no system include paths, no `-l` libc).
+For targets containing `none`, `-elf`, `eabi`, or `baremetal`, DCR automatically:
+
+1. **Disables default flags** — no system include paths, no `-l` libc
+2. **Injects `-ffreestanding`** at compile time and `-nostdlib -static` at link time
+
+You can also enable freestanding mode explicitly:
+
+```toml
+[build]
+freestanding = true
+```
 
 ```bash
 dcr build --target aarch64-none-elf

docs/reference/dcr-toml.mdx

@@ -64,7 +64,7 @@ author = "John Doe"
 | `compiler` | `"clang"` | Preferred compiler |
 | `kind` | `"bin"` | `bin`, `staticlib`, `sharedlib`, `efi`, `elf`, `none`, `custom` |
 | `target` | host | Target triple for cross-compilation |
-| `platform` | `"native"` | `native`, `efi`, `freestanding` |
+| `platform` | `"native"` | `native`, `efi` |
 | `cflags` | `[]` | Additional C/C++/ASM flags |
 | `ldflags` | `[]` | Additional linker flags |
 | `filename` | `""` | Custom output file name |
@@ -77,6 +77,14 @@ author = "John Doe"
 | `clean` | `[]` | Glob patterns for custom clean paths |
 | `out_dir` | `""` | Custom output directory |
 | `workspace_only` | `false` | Workspace-only, not built standalone |
+| `freestanding` | `false` | Compile in freestanding mode (`-ffreestanding` + `-nostdlib -static`) |
+| `opt_level` | `"0"` (debug) / `"3"` (release) | Optimization level: `0`-`3`, `"s"`, `"z"` |
+| `debug` | `true` (debug) / `false` (release) | Emit debug symbols (`-g`) |
+| `lto` | `false` | Link-time optimization (`-flto` for both compiler and linker) |
+| `strip` | `false` | Strip symbols from output (`-s` in ldflags) |
+| `warnings` | `["all", "extra"]` (debug) / `[]` (release) | Warning flags (e.g. `"all"`, `"extra"`, `"pedantic"`) |
+| `panic` | `""` | Panic strategy: `"abort"` disables exceptions and unwind tables |
+| `codegen-units` | `""` | Max parallel compilation jobs (`"0"` = auto) |
 
 Settings from raw config (not in typed struct):
 - `pkg_config` — list of pkg-config packages