pkg-config overrides for RHEL 7 and CentOS 7

RHEL 7 and CentOS 7 do not provide pkg-config .pc files for Tcl/Tk. The OpenSSL 1.1.1 pkg-config file is named openssl11.pc and not picked up by Python's configure script.

To build Python with system Tcl/Tk libs and OpenSSL 1.1 package, first install the developer packages and the pkgconfig package with pkg-config command.

sudo yum install pkgconfig 'tcl-devel >= 8.5.12' 'tk-devel >= 8.5.12' openssl11-devel

The run configure with PKG_CONFIG_PATH environment variable.

PKG_CONFIG_PATH=Misc/rhel7 ./configure -C