(1) It fails to find /usr/include/netpbm/ppm.h from media-libs/netpbm (looking instead for /usr/include/ppm.h). Configuring this correctly with --with-ppm_incdir (instead of the unsupported --with-libppm) only partially helps: the configure script now detects it, but the (broken) Makefile doesn't pass the appropriate -I option to the compiler, leading to a compile error. Using flag-o-matic and adding append-flags -I/usr/include/netpbm in addition to --with-ppm_incdir=/usr/include/netpbm appears to work. (2) The colormaps and overlays are installed in /usr/share/ncview, but the application is build to look in /usr/lib/ncview. Setting NCVIEW_LIB_DIR when calling emake from src_compile (as already done in src_install) fixes this. (3) 1.93c is out of date; 1.93g is the latest upstream version. Bar the above issues which affect both versions, the ebuild appears to work fine with the new version. Full ebuild patch to follow.
Created attachment 193292 [details, diff] Patch to fix the build issues described in the bug report
Now fixed in 1.93g. Thanks.