CMake fails to generate Makefiles with Sun Studio 12.5 - command-line

Question

I'm working on Solaris 11.3 with Sun Studio 12.5. When I attempt to configure with Cmake out-of-tree, Cmake finishes with configuration errors and does not produce the makefiles. In-tree may be broken, too. But our procedures say to build out-of-tree, so that;' what I do.
I have nearly no Cmake experience. Others contributed the the CMake files, and I struggle with tasks related to them. I'm not sure if I am doing something wrong, if our Cmake files are broken, or if Cmake is not well tested under Solaris.
What is going on with CMake, and how do I fix it?
Here are the links to the Cmake files. I can copy/paste them, but it just takes up a bunch of space. The files are hosted on GitHub so they should always be available.
CMakefileList.txt
cryptopp-config.cmake
Here is Solaris' Cmake version, prior to me installing 3.6.2:
$ cmake --version
cmake version 2.8.6
Below is from Solaris Cmake version 2.8.6.
cryptopp-build$ export CXX=/opt/developerstudio12.5/bin/CC
cryptopp-build$ export CXXFLAGS="-DNDEBUG -g2 -O2 -D__SSE2__ -D__SSE3__ -D__SSSE3__ -D__SSE4_1__ -D__SSE4_2__ -D__AES__ -D__PCLMUL__ -D__RDRND__ -D__RDSEED__ -D__AVX__ -D__AVX2__ -D__BMI__ -D__BMI2__ -D__ADX__ -xarch=avx2_i"
cryptopp-build$ cmake ../cryptopp
-- The CXX compiler identification is unknown
-- Check for working CXX compiler: /bin/c++
-- Check for working CXX compiler: /bin/c++ -- broken
CMake Error at /usr/share/cmake-2.8/Modules/CMakeTestCXXCompiler.cmake:45 (MESSAGE):
The C++ compiler "/bin/c++" is not able to compile a simple test program.
It fails with the following output:
Change Dir: /export/home/test/cryptopp-build/CMakeFiles/CMakeTmp
Run Build Command:/bin/gmake "cmTryCompileExec/fast"
/bin/gmake -f CMakeFiles/cmTryCompileExec.dir/build.make
CMakeFiles/cmTryCompileExec.dir/build
gmake[1]: Entering directory
`/export/home/test/cryptopp-build/CMakeFiles/CMakeTmp'
/usr/bin/cmake -E cmake_progress_report
/export/home/test/cryptopp-build/CMakeFiles/CMakeTmp/CMakeFiles 1
Building CXX object CMakeFiles/cmTryCompileExec.dir/testCXXCompiler.cxx.o
/bin/c++ -DNDEBUG -g2 -O2 -D__SSE2__ -D__SSE3__ -D__SSSE3__ -D__SSE4_1__
-D__SSE4_2__ -D__AES__ -D__PCLMUL__ -D__RDRND__ -D__RDSEED__ -D__AVX__
-D__AVX2__ -D__BMI__ -D__BMI2__ -D__ADX__ -xarch=avx2_i -o
CMakeFiles/cmTryCompileExec.dir/testCXXCompiler.cxx.o -c
/export/home/test/cryptopp-build/CMakeFiles/CMakeTmp/testCXXCompiler.cxx
c++: error: language arch=avx2_i not recognized
c++: error: language arch=avx2_i not recognized
gmake[1]: Leaving directory
`/export/home/test/cryptopp-build/CMakeFiles/CMakeTmp'
gmake[1]: *** [CMakeFiles/cmTryCompileExec.dir/testCXXCompiler.cxx.o] Error
1
gmake: *** [cmTryCompileExec/fast] Error 2
CMake will not be able to correctly generate this project.
Call Stack (most recent call first):
CMakeLists.txt:9 (project)
-- Configuring incomplete, errors occurred!
And:
$ /opt/developerstudio12.5/bin/CC -V
CC: Studio 12.5 Sun C++ 5.14 SunOS_i386 2016/05/31
I built Cmake 3.6.2 from sources and installed in /usr/local to attack the CXX compiler identification is unknown issue, but it appears to be having some troubles. As I said earlier, I'm not a Cmake expert (and I'm not sure how one can mess up a make && sudo make install).
cryptopp-build$ cmake ../cryptopp
CMake Error: Could not find CMAKE_ROOT !!!
CMake has most likely not been installed correctly.
Modules directory not found in
/usr/local/bin
CMake Error: Error executing cmake::LoadCache(). Aborting.
Clearing the cache as suggested by #AndrewHenle results in:
# The project GNUmakefile clears all Cmake artifacts because Cmake cannot seem to do it on its own
$ cd cryptopp
$ git status -s
$
$ cd ..
$ rm -rf cryptopp-build
$ mkdir cryptopp-build
$ cd cryptopp-build
# Using 3.6.2 now
$ cmake ../cryptopp
CMake Error: Could not find CMAKE_ROOT !!!
CMake has most likely not been installed correctly.
Modules directory not found in
/usr/local/bin
CMake Error: Error executing cmake::LoadCache(). Aborting.

Answer 1

So there appeared to be two problems. First was the down level Sun supplied Cmake. There's nothing genius about diagnosing it as "too old".
The second issue was more interesting. It appears the CMake Error: Could not find CMAKE_ROOT !!! was cause by sudo make install Once I switched to sudo gmake install the issue went away.
Here are the bug reports on the issue:
Cmake Issue 16302: Cmake fails to identify Sun Studio 12.5 compiler
Cmake Issue 16303: Cmake fails to produce a working installation on Solaris 11.3