lz4: Fix broken builds when pkg-config is not present but system library is

In commit f91e4863bc1382 we fixed an issue where LZ4_LIBS could be
overwritten in some situations.  But on systems where lz4 is installed on
the system but is lacking pkg-config information, the linker will not know
about the lz4 library when completing the build.

This fixes the issue by explicitly setting LZ4_LIBS to contain -llz4
if pkg-config test was run and failed verifying the installed lz4 version
number.  This also ensures that LZ4_LIBS will not be overwritten if it
has been provided on the ./configure command line.

Signed-off-by: David Sommerseth <davids@openvpn.net>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20171002190732.12531-1-davids@openvpn.net>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg15549.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>

diff --git a/configure.ac b/configure.ac
index 394f5b09df4ec76d5eca37fd0f7678af9edb8fca..6f59baefb4198107afbf7bfd391840e3ca000cd8 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -1093,7 +1093,9 @@ if test "$enable_lz4" = "yes" && test "$enable_comp_stub" = "no"; then
        PKG_CHECK_MODULES([LZ4],
                          [liblz4 >= 1.7.1 liblz4 < 100],
                          [have_lz4="yes"],
-                         [] # If this fails, we will do another test next
+                         [LZ4_LIBS="-llz4"] # If this fails, we will do another test next.
+                                            # We also add set LZ4_LIBS otherwise the
+                                            # linker will not know about the lz4 library
        )
     fi