[gradsusr] Installing grads from source

[Zilore Mumba]

Hello once more. I am seeking help installing grads from source. I have
been able to install 23 of the 25 libraries here
http://cola.gmu.edu/grads/gadoc/supplibs2.html.
The only ones I am yet to install are gadap and cairo only.
When I try to install grads, I am encountering a problem of M_PI (pi) not
being declared. I have tried to decalre but no success. I attach my
config.log and and an extract of the make install output that shows on the
screen. Somehow am not able to write to a makeinstall.log from the command
make && make install.

Assistance will be appreciated.

output of "make && make install"
make && make install
Making all in src
make[1]: Entering directory
'/home/zmumba/grads/supplibs/src/grads-2.2.0/src'
make  all-am
make[2]: Entering directory
'/home/zmumba/grads/supplibs/src/grads-2.2.0/src'
/bin/bash ../libtool  --tag=CC   --mode=compile gcc-7 -DHAVE_CONFIG_H -I.
-I. -I/home/zmumba/grads/supplibs/include
-I/home/zmumba/grads/supplibs/include/cairo
-I/home/zmumba/grads/supplibs/include/freetype2
-I/home/zmumba/grads/supplibs/include   -O -ansi -fPIC -rdynamic -c -o
libgxpCairo_la-gxC.lo `test -f 'gxC.c' || echo './'`gxC.c
libtool: compile:  gcc-7 -DHAVE_CONFIG_H -I. -I.
-I/home/zmumba/grads/supplibs/include
-I/home/zmumba/grads/supplibs/include/cairo
-I/home/zmumba/grads/supplibs/include/freetype2
-I/home/zmumba/grads/supplibs/include -O -ansi -fPIC -rdynamic -c gxC.c
-fPIC -DPIC -o .libs/libgxpCairo_la-gxC.o
gxC.c: In function 'gxCch':
gxC.c:879:27: error: 'M_PI' undeclared (first use in this function); did
you mean '__P'?
   if (rotate) rot = rot + M_PI/2;
                           ^~~~
                           __P
gxC.c:879:27: note: each undeclared identifier is reported only once for
each function it appears in
Makefile:750: recipe for target 'libgxpCairo_la-gxC.lo' failed
make[2]: *** [libgxpCairo_la-gxC.lo] Error 1
make[2]: Leaving directory '/home/zmumba/grads/supplibs/src/grads-2.2.0/src'
Makefile:543: recipe for target 'all' failed
make[1]: *** [all] Error 2
make[1]: Leaving directory '/home/zmumba/grads/supplibs/src/grads-2.2.0/src'
Makefile:454: recipe for target 'all-recursive' failed
make: *** [all-recursive] Error 1
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