Fix pkg-config check for inih and enable Ubuntu 18.04 builds

.github/workflows/build.yml

@@ -21,7 +21,7 @@ jobs:
 
     strategy:
       matrix:
-        os: ['ubuntu-20.04', 'macos-latest']
+        os: ['ubuntu-18.04', 'ubuntu-20.04', 'macos-latest']
         cc: ['gcc', 'clang']
 
     steps:

INSTALL.md

@@ -1,12 +1,12 @@
 Installation instructions for x52pro-linux
 ==========================================
 
-[![Build Status](https://www.travis-ci.org/nirenjan/x52pro-linux.svg?branch=master)](https://www.travis-ci.org/nirenjan/x52pro-linux)
+![Build Status](https://www.github.com/nirenjan/x52pro-linux/actions/workflows/build.yml/badge.svg)
 
 Build has been tested on the following operating systems (x86-64 only):
 
-* Ubuntu 16.04 LTS
 * Ubuntu 18.04 LTS
+* Ubuntu 20.04 LTS
 * OS X 10.13.6
 
 # Prerequisites

configure.ac

@@ -46,7 +46,12 @@ AC_SUBST([LIBUSB_LDFLAGS])
 AC_SUBST([LIBUSB_LIBS])
 
 # Check for libinih
-PKG_CHECK_MODULES([INIH], [inih])
+PKG_CHECK_MODULES([INIH], [inih], [],
+                  [
+                    # Older versions of Ubuntu don't provide a .pc file
+                    AC_CHECK_HEADERS([ini.h])
+                    AC_SEARCH_LIBS([ini_parse], [inih])
+                  ])
 AC_SUBST([INIH_CFLAGS])
 AC_SUBST([INIH_LDFLAGS])
 AC_SUBST([INIH_LIBS])