+# gl_IGNORE_UNUSED_LIBRARIES
+# --------------------------
+# Determines the option to be passed to the C/C++/Fortran compiler, so that it
+# omits unused libraries.
+# Example (on Solaris):
+# $ cc foo.c -lnsl; ldd ./a.out
+# libnsl.so.1 => /lib/libnsl.so.1
+# libc.so.1 => /lib/libc.so.1
+# libmp.so.2 => /lib/libmp.so.2
+# libmd.so.1 => /lib/libmd.so.1
+# libscf.so.1 => /lib/libscf.so.1
+# libdoor.so.1 => /lib/libdoor.so.1
+# libuutil.so.1 => /lib/libuutil.so.1
+# libgen.so.1 => /lib/libgen.so.1
+# libm.so.2 => /lib/libm.so.2
+# $ cc foo.c -lnsl -Wl,-z,ignore; ldd ./a.out
+# libc.so.1 => /lib/libc.so.1
+# libm.so.2 => /lib/libm.so.2
+#
+# Note that the option works only for the C compiler, not for the C++
+# compiler:
+# - Sun C likes '-Wl,-z,ignore'.
+# '-Qoption ld -z,ignore' is not accepted.
+# '-z ignore' is accepted but has no effect.
+# - Sun C++ and Sun Fortran like '-Qoption ld -z,ignore'.
+# '-Wl,-z,ignore' is not accepted.
+# '-z ignore' is accepted but has no effect.
+#
+# Sets and substitutes a variable that depends on the current language:
+# - IGNORE_UNUSED_LIBRARIES_CFLAGS for C
+# - IGNORE_UNUSED_LIBRARIES_CXXFLAGS for C++
+# - IGNORE_UNUSED_LIBRARIES_FFLAGS for Fortran
+#
+# Note that the option works only for direct invocation of the compiler, not
+# through libtool: When libtool is used to create a shared library, it will
+# honor and translate '-Wl,-z,ignore' to '-Qoption ld -z -Qoption ld ignore'
+# if needed, but it will drop a '-Qoption ld -z,ignore' on the command line.
+#