llvm-cov: wrong line coverage count for first line after condition in macro

[ManuelvOK]

In code with conditions in macros, the first line after the condition has the same count as the condition itself even if it is not executed.

llvm-cov show results in the following:

    1|       |# define RET    \
    2|      1|    if (0)      \
    3|      1|      return 1; \
    4|      1|    return 0;
    5|       |
    6|      1|int main() {
    7|      1|    RET
    8|      1|}

With a purple line count 1 in line 2 and a red background on the return 1; in line 3.

Using braces on dedicated lines kind of circumvents the issue:

    1|       |# define RET    \
    2|      1|    if (0)      \
    3|      1|    {           \
    4|      0|      return 1; \
    5|      0|    }           \
    6|      1|    return 0;
    7|       |
    8|      1|int main() {
    9|      1|    RET
   10|      1|}

Again, with a purple line count 1 in line 2, but now the red background spans from { to }.

Removing the macro while containing the backslashes leads to the correct line counts:

    1|      1|int main() {
    2|      1|    if (0)      \
    3|      0|      return 1; \
    4|      1|    return 0;
    5|      1|}

The line count calculation inside and outside macros should be consistent.