Move C++ build dir to build/ subdirectory (#177)

This allows easy grouping of multiple custom build directories under
build/.

Author: nikobockerman

.gitignore

@@ -5,7 +5,7 @@
 .venv/
 __pycache__/
 
-/solvers/cpp/build-*/
+/solvers/cpp/build*/
 /solvers/cpp/CMakeUserPresets*.json
 
 /solvers/rust/target/

solvers/cpp/CMakePresets.json

@@ -5,7 +5,7 @@
       "name": "aoc-base",
       "description": "Base preset used when triggered from aoc. User preset named 'aoc' should inherit this and specify GCC/Clang compiler that can build the project",
       "hidden": true,
-      "binaryDir": "build-aoc",
+      "binaryDir": "build/aoc",
       "inherits": [
         "cmake-conan",
         "ninja",