FreeBSD has different pkg-config dir: /usr/local/libdata/

Make.inc

@@ -12,6 +12,12 @@ bindir = $(prefix)/bin
 libdir = $(prefix)/lib
 includedir = $(prefix)/include
 
+ifeq ($(OS), FreeBSD)
+  pkgconfigdir = $(prefix)/libdata/pkgconfig
+else
+  pkgconfigdir = $(libdir)/pkgconfig
+endif
+
 USEGCC = 1
 USECLANG = 0
 
@@ -91,7 +97,7 @@ ifeq ($(OS), WINNT)
   SONAME_FLAG = -soname
   override CFLAGS_add += -nodefaultlibs
   shlibdir = $(bindir)
- else
+else
   ifeq ($(OS), Darwin)
     SHLIB_EXT = dylib
     SONAME_FLAG = -install_name

Makefile

@@ -62,9 +62,9 @@ openlibm.pc: openlibm.pc.in Make.inc Makefile
 
 install: all openlibm.pc
 	mkdir -p $(DESTDIR)$(shlibdir)
-	mkdir -p $(DESTDIR)$(libdir)/pkgconfig
+	mkdir -p $(DESTDIR)$(pkgconfigdir)
 	mkdir -p $(DESTDIR)$(includedir)/openlibm
 	cp -f -a libopenlibm.$(SHLIB_EXT)* $(DESTDIR)$(shlibdir)/
 	cp -f -a libopenlibm.a $(DESTDIR)$(libdir)/
 	cp -f -a include/openlibm*.h $(DESTDIR)$(includedir)/
-	cp -f -a openlibm.pc $(DESTDIR)$(libdir)/pkgconfig/
+	cp -f -a openlibm.pc $(DESTDIR)$(pkgconfigdir)/