title: Error with inline and Xcode 4.2.1
body: <p>I'm trying to get the <a href="http://cran.r-project.org/web/packages/inline/index.html" rel="noreferrer">inline</a> package working on my macbook.  The following block of code (from the cxxfunction examples) fails:</p>
  
  <pre><code>library(inline)
  fx &lt;- cxxfunction( signature(x = "integer", y = "numeric" ) , '
      return ScalarReal( INTEGER(x)[0] * REAL(y)[0] ) ;
  ' )
  fx( 2L, 5 )
  </code></pre>
  
  <p>With this error:</p>
  
  <pre><code>Error in compileCode(f, code, language = language, verbose = verbose) : 
    Compilation ERROR, function(s)/method(s) not created! make: g++-4.2: No such file or directory
  make: *** [file141b5882.o] Error 1
  </code></pre>
  
  <p>This is strange, because g++ is available:</p>
  
  <pre><code>g++ -v
  Using built-in specs.
  Target: i686-apple-darwin11
  Configured with: /private/var/tmp/llvmgcc42/llvmgcc42-2336.1~22/src/configure --disable-checking --enable-werror --prefix=/Developer/usr/llvm-gcc-4.2 --mandir=/share/man --enable-languages=c,objc,c++,obj-c++ --program-prefix=llvm- --program-transform-name=/^[cg][^.-]*$/s/$/-4.2/ --with-slibdir=/usr/lib --build=i686-apple-darwin11 --enable-llvm=/private/var/tmp/llvmgcc42/llvmgcc42-2336.1~22/dst-llvmCore/Developer/usr/local --program-prefix=i686-apple-darwin11- --host=x86_64-apple-darwin11 --target=i686-apple-darwin11 --with-gxx-include-dir=/usr/include/c++/4.2.1
  Thread model: posix
  gcc version 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2336.1.00)
  
  ls /usr/bin | grep gcc
  gcc
  i686-apple-darwin11-llvm-gcc-4.2
  llvm-gcc
  llvm-gcc-4.2
  </code></pre>
  
  <p>I've running Xcode 4.2.1, R 2.14.0, on Mac OS 10.7.2.</p>