Hi,

the debug build is broken because of the -Werror flag.
In particular there are two warnings that are generating the errors:

• Wdeprecated that comes from the includes of openexr where there is a deprecated use of throw in the function definition. Since it is a dependency the only solution is to add a -Wno-deprecated

• implicit-fallthrough that comes from alembic code here https://github.com/alembic/alembic/blob/master/lib/Alembic/Util/SpookyV2.cpp#L117

switch (remainder)
    {
    case 15:
    d += ((uint64_t)u.p8[14]) << 48;
    case 14:
        d += ((uint64_t)u.p8[13]) << 40;
    case 13:
        d += ((uint64_t)u.p8[12]) << 32;
    case 12:
        d += u.p32[2];
        c += u.p64[0];
        break;
    case 11:
        d += ...

A series of switch-case that (I guess/hope :-) ) intentionally fallthrough (ie no break). There is no easy way to fix this, there are ways to fix it for gcc by annotating the code but it is not compatible with clang. There is a [[fallthrought]] annotation in c++17 for this purpose but obviously it requires to upgrade the minimum version of the standard.
Maybe there is another way more complaint with all compilers that I don't know of.
Again the easy way to fix this is to add a -Wno-error=implicit-fallthrough flag (or fixing the switch if it is a bug! :-) )

In case I'd be happy to make the PR for this.

Thanks!

PS
This only affects non-windows builds as no flags are added for windows debug build