RISC-V non-deterministic build failure likely due to race

RISC-V failed like this:
https://github.com/DynamoRIO/dynamorio/actions/runs/5247579249/jobs/9477922603?pr=6137
```
[ 14%] Building CXX object clients/drcachesim/CMakeFiles/drmemtrace_func_view.dir/tools/func_view.cpp.o
In file included from /home/runner/work/dynamorio/dynamorio/build_riscv64-release-external/cmake/../include/dr_ir_macros.h:53,
from /home/runner/work/dynamorio/dynamorio/build_riscv64-release-external/cmake/../include/dr_api.h:96,
from /home/runner/work/dynamorio/dynamorio/clients/drcachesim/tools/func_view.cpp:38:
/home/runner/work/dynamorio/dynamorio/build_riscv64-release-external/cmake/../include/dr_ir_macros_riscv64.h:365:1: error: unterminated comment
365 | /**
| ^
/home/runner/work/dynamorio/dynamorio/build_riscv64-release-external/cmake/../include/dr_ir_macros_riscv64.h:33: error: unterminated #ifndef
33 | #ifndef _DR_IR_MACROS_RISCV64_H_
|
[ 15%] Checking style with vera++ in core
make[2]: *** [clients/drcachesim/CMakeFiles/drmemtrace_func_view.dir/build.make:76: clients/drcachesim/CMakeFiles/drmemtrace_func_view.dir/tools/func_view.cpp.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:1427: clients/drcachesim/CMakeFiles/drmemtrace_func_view.dir/all] Error 2
make[1]: *** Waiting for unfinished jobs....
```

This is non-deterministic and is likely a race in the build config where some target does not list the header generation as a dependence, leading to it reading the header file while it's being written.