[tools] Fix python DeprecationWarning: invalid escape sequence

The python documentation says "it’s highly recommended that you use raw strings for all but the simplest expressions." (https://docs.python.org/3/library/re.html)

So do that with the attached patch generated by

    sed -i -e "s/re.search('/re.search(r'/g" $(git grep -l 're.search(')

The warning can be seen in e.g. python3.7:

    $ python3.7 -Wd
    >>> import re; re.search('\s', '')
    <stdin>:1: DeprecationWarning: invalid escape sequence \s

Commited on behalf of Marco Falke.
Differential Revision: https://reviews.llvm.org/D57528

llvm-svn: 353707
diff --git a/clang/tools/scan-build-py/libscanbuild/analyze.py b/clang/tools/scan-build-py/libscanbuild/analyze.py
index bac259c..49de387 100644
--- a/clang/tools/scan-build-py/libscanbuild/analyze.py
+++ b/clang/tools/scan-build-py/libscanbuild/analyze.py
@@ -97,7 +97,7 @@
     when compiler wrappers are used. That's the moment when build setup
     check the compiler and capture the location for the build process. """
 
-    return len(args) and not re.search('configure|autogen', args[0])
+    return len(args) and not re.search(r'configure|autogen', args[0])
 
 
 def prefix_with(constant, pieces):