Game does not compile with Clang 6

[gentz]

Spidermonkey currently fails to link with Clang 6, however everything else with minimum tweaking does compile.

Comment #2 has my attempt to upgrade to the spidermonkey from the gecko-dev repository which I have given up on.

Comment #4 has a small patch which compiles everything but spidermonkey with Clang 6

[gentz]

Changes so far: ​https://code.wildfiregames.com/P86

I do plan to separate it into multiple patches... trust me that will happen one day.

Note: I'm pretty sure it brakes building spidermonkey on non-linux OSes, I'll also fix that one day.

[gentz]

I've reuploaded properly here: ​https://code.wildfiregames.com/differential/diff/3856/

[gentz]

I can't be bothered to figure out how proxies work and that sorta puts a stop to upgrading 0ad to use the latest spidermonkey.

Instead I've made it compile spidermonkey 38 with GCC and the rest with clang. See my finished diff: ​https://code.wildfiregames.com/D953

[phosit]

Do we still suport Clang 6?

[Ralph Sennhauser]

From the age of this ticket we can infer this is about adding support for the latest clang version or at least a recent one.

The CI uses either version 7 or 8, so we can say 6 is no longer supported even if it worked (possibly using gcc' stl)

[Stan]

Limit was raised for A26 as it triggered some bad assertion in debug mode, preventing the CI to build.

Refs: r27489, r27100