Fix pattern to account for '_' prefix in syscalls

Bug: http://b/64549471
Test: make
Change-Id: I7ba856a2cad29adbb028f150aeaabb9894e84d6e

libc/include/bits/glibc-syscalls.h

@@ -1,6 +1,15 @@
 /* Generated by gensyscalls.py. Do not edit. */
 #ifndef _BIONIC_BITS_GLIBC_SYSCALLS_H_
 #define _BIONIC_BITS_GLIBC_SYSCALLS_H_
+#if defined(__NR__llseek)
+  #define SYS__llseek __NR__llseek
+#endif
+#if defined(__NR__newselect)
+  #define SYS__newselect __NR__newselect
+#endif
+#if defined(__NR__sysctl)
+  #define SYS__sysctl __NR__sysctl
+#endif
 #if defined(__NR_accept)
   #define SYS_accept __NR_accept
 #endif

libc/tools/gensyscalls.py

@@ -568,7 +568,7 @@ class State:
 
         # Collect the set of all syscalls for all architectures.
         syscalls = set()
-        pattern = re.compile(r'^\s*#\s*define\s*__NR_([a-z]\S+)')
+        pattern = re.compile(r'^\s*#\s*define\s*__NR_([a-z_]\S+)')
         for unistd_h in ["kernel/uapi/asm-generic/unistd.h",
                          "kernel/uapi/asm-arm/asm/unistd.h",
                          "kernel/uapi/asm-arm/asm/unistd-common.h",