opus: fix opus.pc pkg-config file for static builds (#1380)

The generated opus.pc file results in undefined symbols during ffmpeg's
configure tests.  libm is not getting added to the link line as
required.  The opus.pc file needs to include -lm in the Libs instead of
Libs.private when generating *only* a static library.

diff --git a/contrib/libopus/A00-static-pkg-config.patch b/contrib/libopus/A00-static-pkg-config.patch
new file mode 100644 (file)
index 0000000..70ef326
--- /dev/null
+++ b/contrib/libopus/A00-static-pkg-config.patch
@@ -0,0 +1,38 @@
+diff -ur opus-1.2.1.orig/configure.ac opus-1.2.1/configure.ac
+--- opus-1.2.1.orig/configure.ac       2017-06-26 11:06:46.000000000 -0700
++++ opus-1.2.1/configure.ac    2018-06-01 17:00:15.140159087 -0700
+@@ -812,6 +812,13 @@
+   AC_DEFINE([ENABLE_UPDATE_DRAFT], [1], [Enable bitstream changes from draft-ietf-codec-opus-update])
+ ])
+ 
++AS_IF([test "$enable_shared" = "no"], [
++    LIBM_SHARED=""
++    LIBM_STATIC="$LIBM"
++], [
++    LIBM_SHARED="$LIBM"
++    LIBM_STATIC=""
++])
+ 
+ saved_CFLAGS="$CFLAGS"
+ CFLAGS="$CFLAGS -fvisibility=hidden"
+@@ -843,6 +850,8 @@
+ AC_CHECK_FUNCS([__malloc_hook])
+ 
+ AC_SUBST([PC_BUILD])
++AC_SUBST([LIBM_SHARED])
++AC_SUBST([LIBM_STATIC])
+ 
+ AC_CONFIG_FILES([
+     Makefile
+diff -ur opus-1.2.1.orig/opus.pc.in opus-1.2.1/opus.pc.in
+--- opus-1.2.1.orig/opus.pc.in 2017-06-15 15:24:07.000000000 -0700
++++ opus-1.2.1/opus.pc.in      2018-06-01 17:00:26.500350502 -0700
+@@ -11,6 +11,6 @@
+ Version: @VERSION@
+ Requires:
+ Conflicts:
+-Libs: -L${libdir} -lopus
+-Libs.private: @LIBM@
++Libs: -L${libdir} -lopus @LIBM_STATIC@
++Libs.private: @LIBM_SHARED@
+ Cflags: -I${includedir}/opus