title: CPP fails sanity check on Mac
body: <p>I’ve searched everywhere and can’t find how to solve this compile problem on my Mac:   </p>
  
  <p><strong>C preprocessor "/lib/cpp" fails sanity check</strong></p>
  
  <p>Update:  I'm trying to compile psqlodbc with ./configure  I get the following:  </p>
  
  <p>configure: error: C preprocessor "/lib/cpp" fails sanity check</p>
  
  <p>Would someone be so kind as to tell me what to check to begin sorting out what could be wrong?  I have read that the problem is usually caused by multiple versions of the compiler and XCode. But, I have no idea how to even begin. Thanks!</p>
  
  <p>Here is my output:</p>
  
  <pre><code>checking for a BSD-compatible install... /usr/bin/install -c
  checking whether build environment is sane... yes
  checking for a thread-safe mkdir -p... config/install-sh -c -d
  checking for gawk... no
  checking for mawk... no
  checking for nawk... no
  checking for awk... awk
  checking whether make sets $(MAKE)... yes
  checking whether make supports nested variables... yes
  checking whether to enable maintainer-specific portions of Makefiles... no
  checking for gcc... gcc
  checking whether the C compiler works... yes
  checking for C compiler default output file name... a.out
  checking for suffix of executables... 
  checking whether we are cross compiling... no
  checking for suffix of object files... o
  checking whether we are using the GNU C compiler... yes
  checking whether gcc accepts -g... yes
  checking for gcc option to accept ISO C89... none needed
  checking whether gcc understands -c and -o together... yes
  checking for style of include used by make... GNU
  checking dependency style of gcc... gcc3
  checking -Wall is a valid compile option... yes
  ./configure: line 4392: /usr/local/iODBC: is a directory
  ./configure: line 4395: /usr/local/iODBC: is a directory
  configure: using  
  checking last argument to SQLColAttribute is SQLLEN *... no
  checking for pg_config... no
  checking for prove... prove
  checking build system type... x86_64-apple-darwin17.5.0
  checking host system type... x86_64-apple-darwin17.5.0
  checking how to print strings... printf
  checking for a sed that does not truncate output... /usr/bin/sed
  checking for grep that handles long lines and -e... /usr/bin/grep
  checking for egrep... /usr/bin/grep -E
  checking for fgrep... /usr/bin/grep -F
  checking for ld used by gcc... /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ld
  checking if the linker (/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ld) is GNU ld... no
  checking for BSD- or MS-compatible name lister (nm)... /usr/bin/nm -B
  checking the name lister (/usr/bin/nm -B) interface... BSD nm
  checking whether ln -s works... yes
  checking the maximum length of command line arguments... 196608
  checking whether the shell understands some XSI constructs... yes
  checking whether the shell understands "+="... yes
  checking how to convert x86_64-apple-darwin17.5.0 file names to x86_64-apple-darwin17.5.0 format... func_convert_file_noop
  checking how to convert x86_64-apple-darwin17.5.0 file names to toolchain format... func_convert_file_noop
  checking for /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ld option to reload object files... -r
  checking for objdump... objdump
  checking how to recognize dependent libraries... pass_all
  checking for dlltool... dlltool
  checking how to associate runtime and link libraries... printf %s\n
  checking for ar... ar
  checking for archiver @FILE support... no
  checking for strip... strip
  checking for ranlib... ranlib
  checking command to parse /usr/bin/nm -B output from gcc object... failed
  checking for sysroot... no
  checking for mt... no
  checking if : is a manifest tool... no
  checking for dsymutil... dsymutil
  checking for nmedit... nmedit
  checking for lipo... lipo
  checking for otool... otool
  checking for otool64... no
  checking for -single_module linker flag... no
  checking for -exported_symbols_list linker flag... yes
  checking for -force_load linker flag... no
  checking how to run the C preprocessor... /lib/cpp
  configure: error: in `/Users/tedhtl/Downloads/psqlodbc-10.01.0000':
  configure: error: C preprocessor "/lib/cpp" fails sanity check
  </code></pre>