Added:

- `sharedlib` build kind (shared library output)
- ASM projects (`build.language = "asm"`)
- NASM and GAS backends
- `build.platform` architecture hint for `-march` / `/arch`
- Basic CLI integration tests

docs/dependencies-and-build/compilers-and-linking.md

@@ -5,9 +5,11 @@
 DCR picks a backend from `build.compiler`:
 
 - contains `clang-cl` -> MSVC backend
+- equals `as` or contains `gas` -> GAS backend (standalone assembler)
 - contains `gcc` or `g++` -> GCC backend
 - contains `clang` or `clang++` -> Clang backend
 - equals `cl` or contains `msvc` -> MSVC backend
+- contains `nasm` -> NASM backend
 - otherwise -> Clang backend fallback
 
 ## Compilation model
@@ -16,6 +18,27 @@ DCR picks a backend from `build.compiler`:
 - Each source is compiled to `target/<profile>/obj/<relative-path>.o` (`.obj` on MSVC).
 - Recompile happens when source mtime is newer than object mtime.
 
+## Default build flags
+
+These flags are applied automatically based on profile and compiler backend.
+
+GCC/Clang:
+
+- `debug`: `-O0 -g -Wall -Wextra -fno-omit-frame-pointer -DDEBUG`
+- `release`: `-O3 -DNDEBUG -march=native`
+
+MSVC:
+
+- `debug`: `/Od /Zi /W4 /DDEBUG /Oy-`
+- `release`: `/O2 /DNDEBUG`
+
+## Platform hint
+
+If `build.platform` is set, DCR passes it as an architecture hint:
+
+- GCC/Clang: `-march=<platform>`
+- MSVC: maps to `/arch:*` for known values (`x86`, `i386`, `i486`, `i586`, `i686`, `sse2`, `avx`, `avx2`)
+
 ## Linking
 
 For `kind = "bin"`:
@@ -28,3 +51,9 @@ For `kind = "staticlib"`:
 
 - Linux/macOS (GCC/Clang): `ar rcs` creates `.a` archive.
 - Windows (MSVC): `lib` creates `.lib` archive.
+
+For `kind = "sharedlib"`:
+
+- Linux (GCC/Clang): `-shared` with output `.so`.
+- macOS (Clang): `-dynamiclib` with output `.dylib`.
+- Windows (MSVC): `/LD` with output `.dll`.