[sdf] Fix for PXR_STRICT_BUILD_MODE with wrap of SdfLayer::Traverse

[pmolodo]

Description of Change(s)

This fixes a build issue introduced by:

[sdf] wrap SdfLayer::Traverse.
2357a7b

...when building with PXR_STRICT_BUILD_MODE + gcc 6 + boost 1.61.

The fix is the same applied by:

Locally disable placement-new warnings in later versions of gcc.
898b8c1

Note - this was fixed in boost 1.62:

boostorg/function#9

Since this placement-new problem is only a problem on specific versions of boost, I wonder if we should add a boost-version check to the places where ARCH_PRAGMA_PLACEMENT_NEW is used?

Alternatively, since vfxplatform-CY2019 is already advocating 1.66 (where this is not an issue), I wonder if it might be better to provide a more "general" solution, by doing a check at the CMAKE level... and if PXR_STRICT_BUILD_MODE is used, and we're using gcc 6+, AND we're using boost<1.62, we simply add a "-Wno-placement-new".

Fixes Issue(s)

• Building with PXR_STRICT_BUILD_MODE + gcc-6 + boost-1.61

[jilliene]

Filed as internal issue #USD-5776

[c64kernal]

Hey @elrond79 -- thanks for the fix! We discussed this a bit and we like your suggestion of just checking for gcc 6+ && boost<1.62 to always add the -Wno-placement-new". That way we have a centralized place to remove the change once we update our minimum required version of boost. Does that sound good? Thanks again!

[pmolodo]

Agreed - I like that solution better too. Closing this in favor of:

#1081

[c64kernal]

Thanks so much @elrond79, we'll have a look at #1081 as soon as we can!