[OpenMP] update strings output of libomp.so [NFC]

[kkwli0]

Summary

Currently, the output of the strings command on libomp.so shows:

@(#) Intel(R) OMP alternative compiler support: yes
@(#) Intel(R) OMP API version: 5.0 (201611)
@(#) Intel(R) OMP lock type: run time selectable
@(#) $Revision: 481659 $
@(#) Intel(R) OMP Fortran __cdecl OMP support: yes
@(#) Intel(R) OMP Fortran "extra" OMP support: yes
@(#) Intel(R) OMP performance library (dynamic) ver. 5.0.20140926
@(#) Intel(R) OMP
@(#) Intel(R) OMP version: 5.0.20140926
@(#) Intel(R) OMP library type: performance
@(#) Intel(R) OMP link type: dynamic
@(#) Intel(R) OMP build time: no_timestamp
@(#) Intel(R) OMP build compiler: Clang 10.0

This patch is to change 'Intel(R)' to 'LLVM'.

[jdoerfert]

LGTM. Nit: Your commit message ends with an } again ;)

openmp/runtime/src/kmp_version.h

/* Using "magic" prefix in all the version strings is rather convenient to get
    static version info from binaries by using standard utilities "strings" and
    "grep", e. g.:
         $ strings libomp.so | grep "@(#)"
    gives clean list of all version strings in the library. Leading zero helps
    to keep version string separate from printable characters which may occurs
    just before version string. */
 #define KMP_VERSION_MAGIC_STR "\x00@(#) "
 #define KMP_VERSION_MAGIC_LEN 6 // Length of KMP_VERSION_MAGIC_STR.
-#define KMP_VERSION_PREF_STR "Intel(R) OMP "
+#define KMP_VERSION_PREF_STR "LLVM OMP "
 #define KMP_VERSION_PREFIX KMP_VERSION_MAGIC_STR KMP_VERSION_PREF_STR
 
 /* declare all the version string constants for KMP_VERSION env. variable */
 extern int const __kmp_version_major;
 extern int const __kmp_version_minor;
 extern int const __kmp_version_build;
 extern int const __kmp_openmp_version;
 extern char const