MLECO-6389: Including cmath header in math library
Fix for some third party toolchains failing to compile the math library without explicitly including the cmath header.
A trivial non-related doumentation fix to say that LLVM or Clang based toolchains may not work for ExecuTorch either. Currently, only Arm GNU Embedded Toolchain works with this flow.
Change-Id: I12889d796886fb0532002c01b1b603982c926e31 Signed-off-by: Kshitij Sisodia kshitij.sisodia@arm.com