Build fails on Solaris 10 (pkgsrc) with missing libproc.h

[ajacocks]

Building on Solaris 10, using gcc-9.3.0, fails with the following:

depbase=`echo AvailableColumnsPanel.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`; gcc -DHAVE_CONFIG_H -I.  -DNDEBUG  -I/usr/pkg/include/ncurses -I/usr/pkg/include -std=c99 -pedantic -Wall -Wcast-align -Wcast-qual -Wextra -Wfloat-equal -Wformat=2 -Winit-self -Wmissing-format-attribute -Wmissing-noreturn -Wmissing-prototypes -Wpointer-arith -Wshadow -Wstrict-prototypes -Wundef -Wunused -Wwrite-strings -Wnull-dereference -D_XOPEN_SOURCE_EXTENDED  -DSYSCONFDIR="\"/usr/pkg/etc\""  -I"./solaris" -O2 -I/usr/pkg/include/ncurses -I/usr/pkg/include -MT AvailableColumnsPanel.o -MD -MP -MF $depbase.Tpo -c -o AvailableColumnsPanel.o AvailableColumnsPanel.c && mv -f $depbase.Tpo $depbase.Po
In file included from AvailableColumnsPanel.c:23:
./solaris/Platform.h:18:10: fatal error: libproc.h: No such file or directory
   18 | #include <libproc.h>
      |          ^~~~~~~~~~~
compilation terminated.
*** Error code 1

Stop.
bmake[1]: stopped making "all-am" in /export/home/ajacocks/src/pkgsrc/sysutils/htop/work/htop-3.3.0
*** Error code 1

Stop.
bmake: stopped making "all" in /export/home/ajacocks/src/pkgsrc/sysutils/htop/work/htop-3.3.0
*** Error code 1

Stop.
bmake[1]: stopped making "install" in /export/home/ajacocks/src/pkgsrc/sysutils/htop
*** Error code 1

Stop.
bmake: stopped making "install" in /export/home/ajacocks/src/pkgsrc/sysutils/htop

I searched for libproc.h, but I found a bunch of references to libproc.h being a private header on Solaris.

I've attached the entire build log, below:

compile.log