title: a configure's options such as "--extra-cflags" --- I am confused
body: <pre><code>    # configure for i386 build
  ./configure \
  --cc=/Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin/gcc \
  --as='gas-preprocessor.pl /Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin/gcc' \
  --sysroot=/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator4.3.sdk \
  --extra-ldflags=-L/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator4.3.sdk/usr/lib/system \
  --target-os=darwin \
  --arch=i386 \
  --cpu=i386 \
  --extra-cflags='-arch i386' \
  --extra-ldflags='-arch i386' \
  --prefix=compiled/i386 \
  --enable-cross-compile \
  --disable-armv5te \
  --disable-ffmpeg \
  --disable-ffplay \
  --disable-ffserver \
  --disable-ffprobe \
  --disable-doc
  </code></pre>
  
  <p>the below will build ffmpeg static libraries for i386. but i don't know about the option's means such as "--extra-cflags"、"--extra-ldflags"、"--sysroot="、"--as=". </p>
  
  <p>who can tell me about those options mean ? where i can find the details explanation？</p>
  
  <p>thanks . I am waitting for your help.</p>