Fix HL2SDK manifests lookup

[akxcv]

POV: tried to build a project copied from s2_sample_mm project

Issue: it tried to look up manifests in the project folder, no matter what's specified in --hl2sdk-manifests.

Traceback (most recent call last):
  File "C:\Users\ak\AppData\Local\Programs\Python\Python310\lib\site-packages\ambuild2\frontend\v2_2\prep.py", line 156, in Configure
    if not cm.generate(options.generator):
  File "C:\Users\ak\AppData\Local\Programs\Python\Python310\lib\site-packages\ambuild2\frontend\context_manager.py", line 93, in generate
    self.parseBuildScripts()
  File "C:\Users\ak\AppData\Local\Programs\Python\Python310\lib\site-packages\ambuild2\frontend\v2_2\context_manager.py", line 50, in parseBuildScripts
    self.execContext(cx)
  File "C:\Users\ak\AppData\Local\Programs\Python\Python310\lib\site-packages\ambuild2\frontend\v2_2\context_manager.py", line 148, in execContext
    exec(code, scriptGlobals)
  File "D:\dev\csgo\whitelist\AMBuildScript", line 296, in <module>
    MMSPlugin.detectSDKs()
  File "D:\dev\csgo\whitelist\AMBuildScript", line 114, in detectSDKs
    SdkHelpers.findSdks(builder, self.all_targets, sdk_list)
  File "D:\dev\csgo\metamod-source\hl2sdk-manifests\SdkHelpers.ambuild", line 23, in findSdks
    for sdk_name, sdk in SdkHelpers.getSdks(builder):
  File "D:\dev\csgo\metamod-source\hl2sdk-manifests\SdkHelpers.ambuild", line 126, in getSdks
    for sdk_manifest in os.listdir(sdk_manifest_dir):
FileNotFoundError: [WinError 3] The system cannot find the path specified: 'D:\\dev\\csgo\\whitelist\\hl2sdk-manifests\\manifests'
Configure failed: [WinError 3] The system cannot find the path specified: 'D:\\dev\\csgo\\whitelist\\hl2sdk-manifests\\manifests'

[psychonic]

Sorry for the delay on this. At a glance it seemed fine, but we can't rely on there being an hl2sdk-manifests option because that is up to the consumer of hl2sdk-manifests. For example, Metamod:Source doesn't implement an option for it because it uses an in-tree submodule, giving it a known path without need for configuration.

I suggest that approach be used for plugins as well, even though there's not a great way for the s2 sample plugin in the MM:S tree to do so with the way it is nested. If there is confusion on that side, we can move the sample to its own repo as a more full example.

As for working around that issue on the side of this repo, this change could instead look up the path of the current file (SdkHelpers.ambuild) and deduce the hl2sdk-manifests path from that, as it lives under that directory.

[akxcv]

Sorry for the delay on this. At a glance it seemed fine, but we can't rely on there being an hl2sdk-manifests option because that is up to the consumer of hl2sdk-manifests. For example, Metamod:Source doesn't implement an option for it because it uses an in-tree submodule, giving it a known path without need for configuration.

I suggest that approach be used for plugins as well, even though there's not a great way for the s2 sample plugin in the MM:S tree to do so with the way it is nested. If there is confusion on that side, we can move the sample to its own repo as a more full example.

As for working around that issue on the side of this repo, this change could instead look up the path of the current file (SdkHelpers.ambuild) and deduce the hl2sdk-manifests path from that, as it lives under that directory.

What do you think about respecting the --hl2sdk-manifests option if it is provided, and falling back to the default path in case this option is missing? To me, this behaviour seems quite straightforward, and we could explicitly document that option for extra clarity.

Though, I admit that it feels wrong that this repo seems to be in charge of looking itself up.