ilbc: moved source extraction in prepare() function; added missing glibc depend

ilbc/PKGBUILD

@@ -1,11 +1,12 @@
 # Contributor: Maurizio Porrato <maurizio.porrato@gmail.com>
 pkgname=ilbc
 pkgver=rfc3951
-pkgrel=5
+pkgrel=6
 arch=(i686 x86_64)
 pkgdesc="A free speech codec suitable for robust VoIP"
 url="http://www.ilbcfreeware.org/"
 license=('custom')
+depends=('glibc')
 makedepends=('awk')
 options=(strip)
 source=(http://www.ietf.org/rfc/rfc3951.txt
@@ -17,12 +18,16 @@ md5sums=('984affd9bf2053064d744a2ccec82289'
          '833675ff45c04be62bc9d6b2fb6fa508'
          'b738390e4108560b8b593454607ddc2b')
 
-build() {
+prepare() {
   rm -rf ${srcdir}/${pkgname}-${pkgver}
   mkdir ${srcdir}/${pkgname}-${pkgver}
   cp ${srcdir}/Makefile ${srcdir}/${pkgname}-${pkgver}
   cd ${srcdir}/${pkgname}-${pkgver}
   awk -f ${srcdir}/extract-cfile.txt ${srcdir}/rfc3951.txt  
+}
+
+build() {
+  cd ${srcdir}/${pkgname}-${pkgver}
   make
 }