Don't pollute Libs with internal bits like libcrypt.

https://bugs.gentoo.org/811765
https://sources.debian.org/patches/apr/1.7.2-2/fix-apr.pc.patch/
https://sources.debian.org/patches/apr/1.7.2-2/omit_extra_libs.patch/

From: <tfheen@debian.org>
Subject: No description.

--- a/apr.pc.in
+++ b/apr.pc.in
@@ -7,5 +7,6 @@
 Name: APR
 Description: The Apache Portable Runtime library
 Version: @APR_DOTTED_VERSION@
-Libs: -L${libdir} -l@APR_LIBNAME@ @EXTRA_LIBS@
-Cflags: @EXTRA_CPPFLAGS@ @EXTRA_CFLAGS@ -I${includedir}
+Libs: -L${libdir} -l@APR_LIBNAME@
+Libs.private: @EXTRA_LIBS@
+Cflags: @EXTRA_CPPFLAGS@ -I${includedir}

From: Stefan Fritsch <sf@debian.org>
Subject: #463399

--- a/apr-config.in
+++ b/apr-config.in
@@ -36,7 +36,7 @@ SHELL="@SHELL@"
 CPPFLAGS="@EXTRA_CPPFLAGS@"
 CFLAGS="@EXTRA_CFLAGS@"
 LDFLAGS="@EXTRA_LDFLAGS@"
-LIBS="@EXTRA_LIBS@"
+LIBS=""
 EXTRA_INCLUDES="@EXTRA_INCLUDES@"
 SHLIBPATH_VAR="@shlibpath_var@"
 APR_SOURCE_DIR="@apr_srcdir@"