CompilerManager: Cannot extract standard include paths.

[thwilloch-stryde]

Describe the bug~
Lot of spurious errors consistent with not finding standard include files.

A clear and concise description of what the bug is.

To Reproduce
Start rdm
In emacs make a change to a source file and save.
See in the rdm output the message
CompilerManager: Cannot extract standard include paths.

See lots of errors consistent with not finding include files.
Like:
Semantic Issue: member reference base type 'istream' (aka 'int') is not a structure or union
Semantic Issue: type 'string' (aka 'basic_string') does not provide a subscript operator

Expected behavior
A clear and concise description of what you expected to happen.
Not to see CompilerManager: Cannot extract standard include paths.
Not to get all refereces to stream and string reslult in error messages.

Screenshots/Backtrace
If applicable, add screenshots or/and a backtrace.

Environment (please complete the following information):

• OS/Version: Red Hat Enterprise Linux release 8.9 (Ootpa)

• RTags(rdm,rc): 2.41.135

• Emacs: 26.1

• LLVM/Clang:16.0.6

Additional context
rtags has worked for me for the last two years. What caused the change I do not know.
I have updateted clang and rtags often.

Seems that adding all the include files explicitly fixes the problem:

Starting rdm as

-I /usr/lib/gcc/x86_64-redhat-linux/8/../../../../include/c++/8 -I /usr/lib/gcc/x86_64-redhat-linux/8/../../../../include/c++/8/x86_64-redhat-linux -I /usr/lib/gcc/x86_64-redhat-linux/8/../../../../include/c++/8/backward -I /usr/lib/gcc/x86_64-redhat-linux/8/include -I /usr/local/include -I /usr/include

works.

And adding the same to emacs variable rtags-rdm-includes also works.

I am using ccache, do not know if that can mess things up.
But it has worked for me the last two years.

[thwilloch-stryde]

It is indeed the ccache that is the issue.
Stepping through rdm with debugger I found that ccache returned the error:
mString = "ccache: error: Could not find compiler "c++" in PATH\n"}

So I assume rdm messes with the PATH before it calls the compiler

PATH= /usr/lib64/ccache/c++ -x c++ -v -E -dM - </dev/null
ccache: error: Could not find compiler "c++" in PATH

This has worked for me for years , so this must be some recent change