iOS: invoke configure directly in script

It seems this is a simpler strategy for invoking the configure
script for iOS. Well, that's the theory. Now, let's see whether
this also works in practice.

Makefile.am

@@ -1 +1 @@
-bin_SCRIPTS = cross-ios
+bin_SCRIPTS = cross-configure-ios

configure.ac

@@ -1,5 +1,5 @@
-AC_INIT([cross], [0.1.0])
-AC_CONFIG_SRCDIR([cross-ios])
+AC_INIT([cross], [0.2.0])
+AC_CONFIG_SRCDIR([cross-configure-ios])
 AM_INIT_AUTOMAKE([foreign])
 AC_PROG_INSTALL
 AC_CONFIG_FILES([Makefile])

cross-ios → cross-configure-ios

@@ -1,7 +1,7 @@
 #!/bin/sh
 set -e
 if [ $# -lt 1 ]; then
-  echo "$0 i386|x86_64|armv7s|arm64 [command [args...]]" 1>&2
+  echo "$0 i386|x86_64|armv7s|arm64 [args...]" 1>&2
   exit 1
 fi
 PKG_ARCH=$1
@@ -35,11 +35,4 @@ export CPPFLAGS="-arch ${PKG_ARCH} -isysroot $(xcrun -sdk ${PLATFORM} --show-sdk
 export CFLAGS="-O2 -arch ${PKG_ARCH} $MINVERSION -isysroot $(xcrun -sdk ${PLATFORM} --show-sdk-path) $CFLAGS"
 export CXXFLAGS="-O2 -arch ${PKG_ARCH} $MINVERSION -isysroot $(xcrun -sdk ${PLATFORM} --show-sdk-path) $CXXFLAGS"
 export LDFLAGS="-arch ${PKG_ARCH} $MINVERSION -isysroot $(xcrun -sdk ${PLATFORM} --show-sdk-path) $LDFLAGS"
-export PKG_CONFIGUREFLAGS
-export PKG_OS="ios"
-export PKG_ARCH
-if [ $# -gt 0 ]; then
-  $@
-else
-  env
-fi
+./configure $PKG_CONFIGUREFLAGS $@