FS-6293: fix mod_silk srcdir build

libs/silk/Makefile.am

-AM_CFLAGS = -Isrc -Iinterface -fPIC -O3
+AM_CFLAGS = -Isrc -I$(abs_srcdir)/src -Iinterface -I$(abs_srcdir)/interface -fPIC -O3
 AUTOMAKE_OPTIONS = gnu
 NAME = libSKP_SILK_SDK
 AM_CPPFLAGS = $(AM_CFLAGS)

libs/silk/configure.ac

@@ -22,5 +22,11 @@ AC_TYPE_SIZE_T
 AC_FUNC_MALLOC
 AC_CHECK_LIB([m],[pow])
 
+# Absolute source/build directory
+abs_srcdir=`(cd $srcdir && pwd)`
+abs_builddir=`pwd`
+AC_SUBST(abs_srcdir)
+AC_SUBST(abs_builddir)
+
 AC_CONFIG_FILES([Makefile])
 AC_OUTPUT

src/mod/codecs/mod_silk/Makefile.am

@@ -14,5 +14,6 @@ mod_silk_la_LDFLAGS  = -avoid-version -module -no-undefined -shared
 BUILT_SOURCES=$(SILK_LA)
 
 $(SILK_LA): $(SILK_DIR)/.update	
-	cd $(SILK_BUILDDIR) && ./configure --disable-shared && make clean && $(MAKE)
+	mkdir -p $(SILK_BUILDDIR)
+	cd $(SILK_BUILDDIR) && $(DEFAULT_VARS) $(SILK_DIR)/configure $(DEFAULT_ARGS) --srcdir=$(SILK_DIR) --disable-shared && make clean && $(MAKE)
 	$(TOUCH_TARGET)