use __strchrnul instead of strchr and strlen in execvpe
The result is the same but takes less code.
Note that __execvpe calls getenv which calls __strchrnul so even
using static output the size of the executable won't grow.
diff --git a/src/process/execvp.c b/src/process/execvp.c
index 1fdf036..ef3b9dd 100644
--- a/src/process/execvp.c
+++ b/src/process/execvp.c
@@ -28,8 +28,7 @@
for(p=path; ; p=z) {
char b[l+k+1];
- z = strchr(p, ':');
- if (!z) z = p+strlen(p);
+ z = __strchrnul(p, ':');
if (z-p >= l) {
if (!*z++) break;
continue;