Gentoo uses non-standard naming for slotted iniparser:4 and it
does not have a pkg-config file (ideally should be unslotted).
Cava can use iniparser:0 as well but <3.2 forces legacy mode.

See also: https://bugs.gentoo.org/933610
--- a/configure.ac
+++ b/configure.ac
@@ -424,5 +424,5 @@
 
-AC_CHECK_LIB(iniparser,iniparser_load, have_iniparser=yes, have_iniparser=no)
+AC_CHECK_LIB(iniparser4,iniparser_load, have_iniparser=yes, have_iniparser=no)
     if [[ $have_iniparser = "yes" ]] ; then
-    LIBS="$LIBS -liniparser"
+    LIBS="$LIBS -liniparser4"
     if [[ $build_mac = "yes" ]] ; then