rofi-calc: Problems installing

Hello, I’m having issues trying to install. Couldn’t find a better place to ask, so here goes:

OS: Ubuntu 18.04.1 LTS rofi version: Version: 1.5.0 (installed from apt) Configuration file: /home/george/.config/rofi/config (not created by default, does not exist)

Installation steps:

>>cd <installation_dir_under_usr_home>
>>git clone <this repo url>

Then:

>>autoreconf -i
aclocal: warning: couldn't open directory 'm4': No such file or directory
libtoolize: putting auxiliary files in '.'.
libtoolize: copying file './ltmain.sh'
libtoolize: putting macros in AC_CONFIG_MACRO_DIRS, 'm4'.
libtoolize: copying file 'm4/libtool.m4'
libtoolize: copying file 'm4/ltoptions.m4'
libtoolize: copying file 'm4/ltsugar.m4'
libtoolize: copying file 'm4/ltversion.m4'
libtoolize: copying file 'm4/lt~obsolete.m4'
configure.ac:32: installing './ar-lib'
configure.ac:17: installing './compile'
configure.ac:53: installing './config.guess'
configure.ac:53: installing './config.sub'
configure.ac:11: installing './install-sh'
configure.ac:11: installing './missing'
Makefile.am: installing './depcomp'

>>mkdir build
>>cd ./build

Finally this fails:

>>../configure
checking for a BSD-compatible install... /usr/bin/install -c
checking whether build environment is sane... yes
checking for a thread-safe mkdir -p... /bin/mkdir -p
checking for gawk... no
checking for mawk... mawk
checking whether make sets $(MAKE)... yes
checking whether make supports nested variables... yes
checking whether make supports nested variables... (cached) yes
checking for style of include used by make... GNU
checking for gcc... gcc
checking whether the C compiler works... yes
checking for C compiler default output file name... a.out
checking for suffix of executables... 
checking whether we are cross compiling... no
checking for suffix of object files... o
checking whether we are using the GNU C compiler... yes
checking whether gcc accepts -g... yes
checking for gcc option to accept ISO C89... none needed
checking whether gcc understands -c and -o together... yes
checking dependency style of gcc... gcc3
checking for gcc option to accept ISO C99... none needed
checking how to run the C preprocessor... gcc -E
checking for grep that handles long lines and -e... /bin/grep
checking for egrep... /bin/grep -E
checking for ANSI C header files... yes
checking for sys/types.h... yes
checking for sys/stat.h... yes
checking for stdlib.h... yes
checking for string.h... yes
checking for memory.h... yes
checking for strings.h... yes
checking for inttypes.h... yes
checking for stdint.h... yes
checking for unistd.h... yes
checking minix/config.h usability... no
checking minix/config.h presence... no
checking for minix/config.h... no
checking whether it is safe to define __EXTENSIONS__... yes
checking for ar... ar
checking the archiver (ar) interface... ar
../configure: line 4734: PKG_PROG_PKG_CONFIG: command not found
../configure: line 4737: syntax error near unexpected token `glib,'
../configure: line 4737: `PKG_CHECK_MODULES(glib,     glib-2.0 >= 2.40 gio-unix-2.0 gmodule-2.0 )'

Launching according to the man page instructions:

Use qalc to get a simple calculator in rofi:

        rofi -show calc -modi "calc:qalc +u8 -nocurrencies"

does not work either: it fails with

failed to execute: 'qalc +8 -nocurrencies'
Error: 'Failed to execute child process "qalc" (No such file or directory)'

Any suggestions? Thanks in advance.