audacity: add missing stdlib flags

Closes: https://trac.macports.org/ticket/56097

audio/audacity/Portfile

@@ -189,8 +189,16 @@ configure.env-append \
 depends_lib-append \
                     port:portmidi
 
+# make sure the C++ stdlib argument is added to the LDFLAGS too
+if {${configure.cxx_stdlib} ne "" && [string match *clang* ${configure.cxx}]} {
+    configure.ldflags-append \
+                    -stdlib=${configure.cxx_stdlib}
+}
+
 build.args-append   V=1 VERBOSE=1
 
+# with everything defined/declared as intended we can now
+# handle the post-patch step with its reinplace statements.
 post-patch {
     set python_bin ${prefix}/bin/python2.7
     reinplace -W ${worksrcpath} "s|@@PYTHON@@|${python_bin}|g" \
@@ -208,6 +216,8 @@ post-patch {
     reinplace -W ${worksrcpath} "s| -Werror||g" \
                                 lib-src/portaudio-v19/configure.in \
                                 lib-src/portaudio-v19/configure
+    reinplace -W ${worksrcpath} "s|@LDFLAGS@|${configure.ldflags}|g" \
+                                lib-src/libvamp/Makefile.in
     platform darwin {
         # audacity 2.1.2 contains C++ files that include system SDK headers and ObjC code on OS X;
         # they must thus be built as ObjC++

audio/audacity/files/libvamp-Makefile-for-osx.diff

@@ -1,8 +1,8 @@
 diff --git a/lib-src/libvamp/Makefile.in b/lib-src/libvamp/Makefile.in
-index 4fc9378..5e6116d 100644
+index 4fc9378b57c70675c0f0243b2598342c4414ccf9..a56a05346e595d73d7189d4b7bcfe89e93bfb1bb 100644
 --- a/lib-src/libvamp/Makefile.in
 +++ b/lib-src/libvamp/Makefile.in
-@@ -100,21 +100,21 @@ INSTALL_PKGCONFIG	  = $(INSTALL_PREFIX)/lib/pkgconfig
+@@ -100,22 +100,23 @@ INSTALL_PKGCONFIG	  = $(INSTALL_PREFIX)/lib/pkgconfig
 
  # Flags required to tell the compiler to create a dynamically loadable object
  #
@@ -30,5 +30,7 @@ index 4fc9378..5e6116d 100644
 +SDK_DYNAMIC_LDFLAGS		= $(DYNAMIC_LDFLAGS)
 +HOSTSDK_DYNAMIC_LDFLAGS	= $(DYNAMIC_LDFLAGS)
 
++LDFLAGS			+= @LDFLAGS@
 
  ### End of user-serviceable parts
+