Determining if the PHYSFS_getPrefDir exist failed with the following output:
Change Dir: /home/naourr/work/instance-0/output/build/supertux-0.5.1/CMakeFiles/CMakeTmp

Run Build Command:"/usr/bin/gmake" "cmTC_e09e2/fast"
gmake[1]: Entering directory '/home/naourr/work/instance-0/output/build/supertux-0.5.1/CMakeFiles/CMakeTmp'
/usr/bin/gmake -f CMakeFiles/cmTC_e09e2.dir/build.make CMakeFiles/cmTC_e09e2.dir/build
gmake[2]: Entering directory '/home/naourr/work/instance-0/output/build/supertux-0.5.1/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_e09e2.dir/CheckSymbolExists.c.o
/home/naourr/work/instance-0/output/host/bin/mips64el-linux-gcc --sysroot=/home/naourr/work/instance-0/output/host/mips64el-buildroot-linux-gnu/sysroot   -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os   -DNDEBUG   -o CMakeFiles/cmTC_e09e2.dir/CheckSymbolExists.c.o   -c /home/naourr/work/instance-0/output/build/supertux-0.5.1/CMakeFiles/CMakeTmp/CheckSymbolExists.c
Linking C executable cmTC_e09e2
/usr/bin/cmake -E cmake_link_script CMakeFiles/cmTC_e09e2.dir/link.txt --verbose=1
/home/naourr/work/instance-0/output/host/bin/mips64el-linux-gcc --sysroot=/home/naourr/work/instance-0/output/host/mips64el-buildroot-linux-gnu/sysroot -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os   -DNDEBUG    -rdynamic CMakeFiles/cmTC_e09e2.dir/CheckSymbolExists.c.o  -o cmTC_e09e2 
CMakeFiles/cmTC_e09e2.dir/CheckSymbolExists.c.o: In function `main':
CheckSymbolExists.c:(.text.startup+0xc): undefined reference to `PHYSFS_getPrefDir'
collect2: error: ld returned 1 exit status
gmake[2]: *** [CMakeFiles/cmTC_e09e2.dir/build.make:87: cmTC_e09e2] Error 1
gmake[2]: Leaving directory '/home/naourr/work/instance-0/output/build/supertux-0.5.1/CMakeFiles/CMakeTmp'
gmake[1]: *** [Makefile:126: cmTC_e09e2/fast] Error 2
gmake[1]: Leaving directory '/home/naourr/work/instance-0/output/build/supertux-0.5.1/CMakeFiles/CMakeTmp'

File /home/naourr/work/instance-0/output/build/supertux-0.5.1/CMakeFiles/CMakeTmp/CheckSymbolExists.c:
/* */
#include </home/naourr/work/instance-0/output/host/mips64el-buildroot-linux-gnu/sysroot/usr/include/physfs.h>

int main(int argc, char** argv)
{
  (void)argv;
#ifndef PHYSFS_getPrefDir
  return ((int*)(&PHYSFS_getPrefDir))[argc];
#else
  (void)argc;
  return 0;
#endif
}

Performing C++ SOURCE FILE Test HAVE_ICONV_CONST failed with the following output:
Change Dir: /home/naourr/work/instance-0/output/build/supertux-0.5.1/CMakeFiles/CMakeTmp

Run Build Command:"/usr/bin/gmake" "cmTC_b214b/fast"
gmake[1]: Entering directory '/home/naourr/work/instance-0/output/build/supertux-0.5.1/CMakeFiles/CMakeTmp'
/usr/bin/gmake -f CMakeFiles/cmTC_b214b.dir/build.make CMakeFiles/cmTC_b214b.dir/build
gmake[2]: Entering directory '/home/naourr/work/instance-0/output/build/supertux-0.5.1/CMakeFiles/CMakeTmp'
Building CXX object CMakeFiles/cmTC_b214b.dir/src.cxx.o
/home/naourr/work/instance-0/output/host/bin/mips64el-linux-g++ --sysroot=/home/naourr/work/instance-0/output/host/mips64el-buildroot-linux-gnu/sysroot    -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os -DHAVE_ICONV_CONST  -DNDEBUG   -o CMakeFiles/cmTC_b214b.dir/src.cxx.o -c /home/naourr/work/instance-0/output/build/supertux-0.5.1/CMakeFiles/CMakeTmp/src.cxx
/home/naourr/work/instance-0/output/build/supertux-0.5.1/CMakeFiles/CMakeTmp/src.cxx:4:9: error: ambiguating new declaration of 'double iconv(iconv_t, char**, size_t*, char**, size_t*)'
  double iconv(iconv_t cd,  char **inbuf, size_t *inbytesleft, char **outbuf, size_t *outbytesleft);
         ^~~~~
In file included from /home/naourr/work/instance-0/output/build/supertux-0.5.1/CMakeFiles/CMakeTmp/src.cxx:2:0:
/home/naourr/work/instance-0/output/host/mips64el-buildroot-linux-gnu/sysroot/usr/include/iconv.h:42:15: note: old declaration 'size_t iconv(iconv_t, char**, size_t*, char**, size_t*)'
 extern size_t iconv (iconv_t __cd, char **__restrict __inbuf,
               ^~~~~
gmake[2]: *** [CMakeFiles/cmTC_b214b.dir/build.make:66: CMakeFiles/cmTC_b214b.dir/src.cxx.o] Error 1
gmake[2]: Leaving directory '/home/naourr/work/instance-0/output/build/supertux-0.5.1/CMakeFiles/CMakeTmp'
gmake[1]: *** [Makefile:126: cmTC_b214b/fast] Error 2
gmake[1]: Leaving directory '/home/naourr/work/instance-0/output/build/supertux-0.5.1/CMakeFiles/CMakeTmp'

Source file was:

	#include <iconv.h>
	// this declaration will fail when there already exists a non const char** version which returns size_t
	double iconv(iconv_t cd,  char **inbuf, size_t *inbytesleft, char **outbuf, size_t *outbytesleft);
	int main() { return 0; }