prereq-build: add missing check for Perl IPC::Cmd

prereq-build: add missing check for Perl IPC::Cmd

OpenSSL fails to compile in Fedora 38 container due to the following:

 Can't locate IPC/Cmd.pm in @INC (you may need to install the IPC::Cmd module) (@INC contains: /openwrt/build_dir/target-x86_64_musl/openssl-3.0.8/util/perl /usr/local/lib64/perl5/5.36 /usr/local/share/perl5/5.36 /usr/lib64/perl5/vendor_perl /usr/share/perl5/vendor_perl /usr/lib64/perl5 /usr/share/perl5 /openwrt/build_dir/target-x86_64_musl/openssl-3.0.8/external/perl/Text-Template-1.56/lib) at /openwrt/build_dir/target-x86_64_musl/openssl-3.0.8/util/perl/OpenSSL/config.pm line 19.
 BEGIN failed--compilation aborted at /openwrt/build_dir/target-x86_64_musl/openssl-3.0.8/util/perl/OpenSSL/config.pm line 19.
 Compilation failed in require at ./Configure line 23.
 BEGIN failed--compilation aborted at ./Configure line 23.

Seems like `dnf install -y perl-IPC-Cmd` fixes the issue.

So lets fix it by checking for Perl IPC::Cmd host module availability.

Signed-off-by: Petr Štetiar <ynezz@true.cz>