Detecting the platform in rpm .spec file - centos

Question

I have a .spec file to build rpm for Fedora, CentOS and Oracle Linux. I need to install a post-uninstall trigger for the kernel package. To achieve that for Oracle Linux, I need to put something like this in my spec file:
%triggerpostun -- kernel-uek
%(cat %{SOURCE1001})
On CentOS, the package is called kernel, and on Fedora it is called kernel-core. My question is, how do I specify the trigger in my spec file in a portable way (so that it works on all of these target platforms), without any duplication?
EDIT: Some information about what I have tried - I tried putting the following in my spec file:
%if 0%{?fedora}
%triggerpostun -- kernel-core
%else
%if 0%{?ol7}
%triggerpostun -- kernel-uek
%else
%triggerpostun -- kernel
%endif
%endif
%(cat %{SOURCE1006})
But on CentOS, this gives me a trigger like this:
triggerpostun scriptlet (using /bin/sh) -- kernel-uek
for filename in /boot/*.ksplice-updates*; do
if [[ -h $filename && ! -e $filename ]]; then
rm $filename
fi
done
which is wrong because the correct package name on CentOS is kernel.
I am complete noob to packaging, so let me know if you need more context to provide suggestion.

Answer 1

I assume the multiple %else are causing problems. I would define the conditions this way:
%if 0%{?fedora}
%define kernelpkgname kernel-core
%endif
%if 0%{?ol7}
%define kernelpkgname kernel-uek
%endif
%if 0%{?rhel} >= 6
%define kernelpkgname kernel
%endif
Then use kernelpkgname variable in the triggerpostun.
%postun
....
%triggerpostun -- %{kernelpkgname}
cat %{SOURCE1006}