php: Support opcache cross compilation

[repk]

Opcache extension configuration tries to detect some shared memory
function by compiling and executing test programs at compile time.
This cannot work when cross compiling.

To workaround that add proper defines to use those functions anyway if
we are cross compiling.

That fixes the following error when using opcache extension on arm:
Fatal Error Unable to allocate shared memory segment of 134217728 bytes

General

• This is a new package and it conforms to the quality requirements

Have the results of the proposed changes been tested?

• I use the packages affected by the proposed changes on a regular basis and confirm this PR works for me
• I generally don't use the affected packages but briefly tested this PR

[ericonr]

You need to revbump the package for it to be rebuilt, which will apply your fix.

[repk]

This has been pushed along #32890