arch/riscv: Adjust compiler flags for scan-build

Clang doesn't understand -march=riscv64imac and -mcmodel=medany, so
don't use them when running the clang static analyzer. On the other
hand, __riscv and __riscv_xlen need to be defined in order to select
some macros in src/arch/riscv/include/arch/encoding.h. __riscv_flen
selects the floating-point paths in src/arch/riscv/misaligned.c.
-mabi is moved with -march for consistency.

A complete list of preprocessor definitions on RISC-V can be found at
https://github.com/riscv/riscv-toolchain-conventions#cc-preprocessor-definitions

With this commit, scan-build produces a useful result on RISC-V.

Change-Id: Ia2eb8c3c2f7eb5ddd47db24b8e5fcd6eaf6c5589
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-on: https://review.coreboot.org/28713
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Philipp Hug <philipp@hug.cx>
Reviewed-by: Martin Roth <martinroth@google.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/arch/riscv/Makefile.inc

@@ -25,7 +25,12 @@ ifeq ($(CONFIG_ARCH_RAMSTAGE_RISCV),y)
 check-ramstage-overlap-regions += stack
 endif
 
-riscv_flags = -I$(src)/arch/riscv/ -mcmodel=$(CONFIG_RISCV_CODEMODEL) -march=$(CONFIG_RISCV_ARCH) -mabi=$(CONFIG_RISCV_ABI)
+riscv_flags = -I$(src)/arch/riscv/
+ifeq ($(CCC_ANALYZER_OUTPUT_FORMAT),)
+riscv_flags += -march=$(CONFIG_RISCV_ARCH) -mabi=$(CONFIG_RISCV_ABI) -mcmodel=$(CONFIG_RISCV_CODEMODEL)
+else
+riscv_flags += -D__riscv -D__riscv_xlen=64 -D__riscv_flen=64
+endif
 
 riscv_asm_flags = -march=$(CONFIG_RISCV_ARCH) -mabi=$(CONFIG_RISCV_ABI)