libarchive "not found" when Compiling Ardour on macOS High Sierra 10.13.6

Question

I'm trying to compile the stable version of Ardour (6.0.0) on macOS High Sierra 10.13.6, which I've obtained via git clone https://github.com/boostorg/boost.git. I've managed to work out the first couple of dependancies, but am now stuck on getting past Ardour detecting libarchive. I also have the latest version of Homebrew (2.3.0) installed.

When I run sudo ./waf configure --boost-include=/usr/local/boost-1.73.0/include CXX=g++-9 CC=gcc-9 to compile Ardour, this is the output:

Setting top to                           : /Users/kjesso/ardour/6.0.70-x86_64 
Setting out to                           : /Users/kjesso/ardour/6.0.70-x86_64/build 
Checking for 'gcc' (C compiler)          : gcc-9 
Checking for 'g++' (C++ compiler)        : g++-9 

Global Configuration 
 * Install prefix                                    : /usr/local 
 * Debuggable build                                  : True 
 * Build documentation                               : False 

Ardour Configuration 
 * Will build against private GTK dependency stack   : no 
 * Will use explicit linkage against libintl in /Users/kjesso/gtk/inst : yes 
 * Will build against private Ardour dependency stack : no 
No Carbon support available for this build

Checking for function 'dlopen' in dlfcn.h            : yes 
Checking for boost library >= 1.56                   : ok 
Checking for program 'pkg-config'                    : /usr/local/bin/pkg-config 
Checking for 'glib-2.0' >= 2.28                      : yes 
Checking for 'gthread-2.0' >= 2.2                    : yes 
Checking for 'glibmm-2.4' >= 2.32.0                  : yes 
Checking for 'sndfile' >= 1.0.18                     : yes 
Checking for 'giomm-2.4' >= 2.2                      : yes 
Checking for 'libcurl' >= 7.0.0                      : yes 
Checking for 'libarchive' >= 3.0.0                   : not found 
The configuration failed
(complete log in /Users/kjesso/ardour/6.0.70-x86_64/build/config.log)

Here is the output from the Ardour build/config.log:

Checking for 'libarchive' >= 3.0.0
['/usr/local/bin/pkg-config', 'libarchive >= 3.0.0', '--cflags', '--libs', 'libarchive']
err: Package libarchive was not found in the pkg-config search path.
Perhaps you should add the directory containing `libarchive.pc'
to the PKG_CONFIG_PATH environment variable
No package 'libarchive' found
Package libarchive was not found in the pkg-config search path.
Perhaps you should add the directory containing `libarchive.pc'
to the PKG_CONFIG_PATH environment variable
No package 'libarchive' found

The libarchive pkgconfig directory does contain the libarchive.pc file:

MacBookPro:ardour kjesso$ ls -al /usr/local/opt/libarchive/lib/pkgconfig
total 8
drwxr-xr-x  3 kjesso  staff  102  7 Jun 22:05 .
drwxr-xr-x  6 kjesso  staff  204 19 May 18:10 ..
-r--r--r--  1 kjesso  staff  378  7 Jun 22:05 libarchive.pc

I've already installed the latest version of libarchive 3.4.3 via homebrew, added the libarchive pkgconfig path to the PKG_CONFIG_PATH environment variable along with the other instructions from the libarchive homebrew install:

libarchive is keg-only, which means it was not symlinked into /usr/local, because macOS already provides this software and installing another version in parallel can cause all kinds of trouble.

If you need to have libarchive first in your PATH run: echo 'export PATH="/usr/local/opt/libarchive/bin:$PATH"' >> /Users/kjesso/.bash_profile

For compilers to find libarchive you may need to set: export LDFLAGS="-L/usr/local/opt/libarchive/lib" export CPPFLAGS="-I/usr/local/opt/libarchive/include"

For pkg-config to find libarchive you may need to set: export PKG_CONFIG_PATH="/usr/local/opt/libarchive/lib/pkgconfig"

Output of PKG_CONFIG_PATH environment variable:

MacBookPro:ardour kjesso$ echo $PKG_CONFIG_PATH
/usr/local/opt/libarchive/lib/pkgconfig/

The path /usr/local/opt/libarchive is a symbolic link to /usr/local/Cellar/libarchive/3.4.3/:

MacBookPro:6.0.70-x86_64 kjesso$ ls -al /usr/local/opt/libarchive
lrwxr-xr-x  1 kjesso  admin  26  7 Jun 22:05 /usr/local/opt/libarchive -> ../Cellar/libarchive/3.4.3

I've searched online, but haven't found anything helpful. Anyone have any idea on why Ardour isn't detecting the latest version 3.4.3 of libarchive?