Problem When Compiling with Slackbuild Script

I have done a full install of slackware 15.0. Previously, I had no problem compiling & installing software using sboui or directly from the Slackbuild script. Lately I have been getting errors. If I try upgrading gtest with sboui, I get the following:

gtest is already installed.
Installed package: gtest-1.10.0-x86_64-4_SBo
Available version: 1.14.0
--2024-02-04 14:24:12--  https://github.com/google/googletest/archive/v1.14.0/googletest-1.14.0.tar.gz 
Resolving github.com (github.com)... 140.82.113.4
Connecting to github.com (github.com)|140.82.113.4|:443... connected.
ERROR: cannot verify github.com's certificate, issued by ‘CN=DigiCert TLS Hybrid ECC SHA384 2020 CA1,O=DigiCert Inc,C=US’:
Unable to locally verify the issuer's authority.
To connect to github.com insecurely, use `--no-check-certificate'.
There was an error downloading the source file.
md5sum: googletest-1.14.0.tar.gz: No such file or directory
Error: md5sum check failed on googletest-1.14.0.tar.gz. Continue anyway? (y/n):

If I try downloading the source & slackbuild tar builds and try running the .Slackbuild script directly, I get:

[ 12%] Building CXX object googletest/CMakeFiles/gtest.dir/src/gtest-all.cc.o
In file included from /usr/include/errno.h:28,
from /usr/include/c++/11.2.0/cerrno:42,
from /usr/include/c++/11.2.0/ext/string_conversions.h:44,
from /usr/include/c++/11.2.0/bits/basic_string.h:6607,
from /usr/include/c++/11.2.0/string:55,
from /usr/include/c++/11.2.0/bits/locale_classes.h:40,
from /usr/include/c++/11.2.0/bits/ios_base.h:41,
from /usr/include/c++/11.2.0/iomanip:40,
from /tmp/SBo/googletest-1.14.0/googletest/include/gtest/gtest.h:54,
from /tmp/SBo/googletest-1.14.0/googletest/src/gtest-all.cc:38:
/usr/include/bits/errno.h:26:11: fatal error: linux/errno.h: No such file or directory
26 | # include 
|             ^~~~~~~~~~~~~~~

Any ideas on how to fix these problems. **UPDATE:**

$ update-ca-certificates
Updating certificates in /etc/ssl/certs...
0 added, 0 removed; done.
Running hooks in /etc/ca-certificates/update.d...
done.

Still get the same error message. And, the headers are installed. In fact, I see several erron.h files in various subdirecitories.

$ ls /var/log/packages/kernel-headers-5.15.117-x86-1  
/var/log/packages/kernel-headers-5.15.117-x86-1  
$ pwd  
/usr/src/linux  
$ find . -name errno.h  
./arch/powerpc/include/uapi/asm/errno.h  
./arch/sparc/include/uapi/asm/errno.h  
./arch/parisc/include/uapi/asm/errno.h  
./arch/x86/include/generated/uapi/asm/errno.h  
./arch/mips/include/asm/errno.h  
./arch/mips/include/uapi/asm/errno.h  
./arch/alpha/include/uapi/asm/errno.h  
./tools/arch/powerpc/include/uapi/asm/errno.h  
./tools/arch/sparc/include/uapi/asm/errno.h  
./tools/arch/parisc/include/uapi/asm/errno.h  
./tools/arch/x86/include/uapi/asm/errno.h  
./tools/arch/mips/include/asm/errno.h  
./tools/arch/mips/include/uapi/asm/errno.h  
./tools/arch/alpha/include/uapi/asm/errno.h  
./tools/bootconfig/include/linux/errno.h  
./tools/include/uapi/asm/errno.h  
./tools/include/uapi/asm-generic/errno.h  
./include/linux/errno.h  
./include/uapi/linux/errno.h  
./include/uapi/asm-generic/errno.h