Document build type options

Summary:
**Pre-submission checklist**
- [x] I've ran the linters locally and fixed lint errors related to the files I modified in this PR. You can install the linters by running `pip install -r requirements-dev.txt && pre-commit install`
- [x] `pre-commit run`

Document the `--build-type` option for the run-getdeps.py build script and refactor the argument definition to eliminate code duplication.

- **docs/docs/build/Building_FBOSS_on_containers.md**: Added comprehensive documentation about build types (Debug, Release, RelWithDebInfo, MinSizeRel) with a table explaining each option
- **docs/docs/platform/Building_Platform_Services.md**: Updated build commands to use `--build-type` flag
- **docs/static/code_snips/*.sh**: Updated all build script examples to use `--build-type` instead of passing `CMAKE_BUILD_TYPE` in `--extra-cmake-defines`

- Updated the `--build-type` help text in run-getdeps.py to include:
  - Concise descriptions of each build type
  - Indication that RelWithDebInfo is the default
  - Removed the outdated "widely supported" comment

- Created a shared `BUILD_TYPE_ARG` kwargs dictionary to define the `--build-type` argument once
- Replaced three duplicate argument definitions in BuildCmd, TestCmd, and GenerateGithubActionsCmd classes
- Reduced code duplication and improved maintainability

- Users now understand what each build type does
- Cleaner syntax: `--build-type MinSizeRel` vs JSON in `--extra-cmake-defines`
- Single source of truth for the argument definition
- Easier to maintain and update in the future

Verified that help output works correctly for all three commands:
- `build --help`
- `test --help`
- `generate-github-actions --help`

X-link: facebook/fboss#842

Reviewed By: joseph5wu

Differential Revision: D93010077

Pulled By: KevinYakar

fbshipit-source-id: d1a0b780c28e8f8fa5ca716326fbcadb244ade87

Author: anna-nexthop

build/fbcode_builder/getdeps.py

@@ -47,6 +47,15 @@ class UsageError(Exception):
     pass
 
 
+# Shared argument definition for --build-type used by multiple commands
+BUILD_TYPE_ARG = {
+    "help": "Set the build type explicitly: Debug (unoptimized, debug symbols), RelWithDebInfo (optimized with debug symbols, default), MinSizeRel (size-optimized, no debug), or Release (optimized, no debug).",
+    "choices": ["Debug", "Release", "RelWithDebInfo", "MinSizeRel"],
+    "action": "store",
+    "default": "RelWithDebInfo",
+}
+
+
 @cmd("validate-manifest", "parse a manifest and validate that it is correct")
 class ValidateManifest(SubCmd):
     def run(self, args):
@@ -881,13 +890,7 @@ def setup_project_cmd_parser(self, parser):
             action="store_true",
             default=False,
         )
-        parser.add_argument(
-            "--build-type",
-            help="Set the build type explicitly.  Cmake and cargo builders act on them. Only Debug and RelWithDebInfo widely supported.",
-            choices=["Debug", "Release", "RelWithDebInfo", "MinSizeRel"],
-            action="store",
-            default=None,
-        )
+        parser.add_argument("--build-type", **BUILD_TYPE_ARG)
 
 
 @cmd("fixup-dyn-deps", "Adjusts dynamic dependencies for packaging purposes")
@@ -969,13 +972,7 @@ def setup_project_cmd_parser(self, parser):
             default=None,
             help="Timeout in seconds for each individual test",
         )
-        parser.add_argument(
-            "--build-type",
-            help="Set the build type explicitly.  Cmake and cargo builders act on them. Only Debug and RelWithDebInfo widely supported.",
-            choices=["Debug", "Release", "RelWithDebInfo", "MinSizeRel"],
-            action="store",
-            default=None,
-        )
+        parser.add_argument("--build-type", **BUILD_TYPE_ARG)
 
 
 @cmd(
@@ -1450,13 +1447,7 @@ def setup_project_cmd_parser(self, parser):
             action="store_true",
             default=False,
         )
-        parser.add_argument(
-            "--build-type",
-            help="Set the build type explicitly.  Cmake and cargo builders act on them. Only Debug and RelWithDebInfo widely supported.",
-            choices=["Debug", "Release", "RelWithDebInfo", "MinSizeRel"],
-            action="store",
-            default=None,
-        )
+        parser.add_argument("--build-type", **BUILD_TYPE_ARG)
         parser.add_argument(
             "--no-build-cache",
             action="store_false",

build/fbcode_builder/getdeps/buildopts.py

@@ -113,10 +113,6 @@ def __init__(
         self.lfs_path = lfs_path
         self.shared_libs = shared_libs
         self.free_up_disk = free_up_disk
-
-        if build_type is None:
-            build_type = "RelWithDebInfo"
-
         self.build_type = build_type
 
         lib_path = None