Fails to build for Opensplice-6.9.210323OSS-armv7l-GCC10

[richardbostock]

GCC 10 requires some of the variables defined in headers to be moved to externs.
_POSIX_PATH_MAX was undefined under GCC10 on ARM.

Attached is a git patch (zipped) for the modifications required to get this to build. Let me know if you want me to upload this as a pull request.

0001-GCC-10-enforces-usage-of-externs-for-global-variable.zip

[ThijsSassen]

@richardbostock thank you, we will take a look at this