Update coq_makefile timing test

This fixes #5675 (in yet another way).

The issue was that `$` (end of string regex) was not properly escaped in
`"`s.

This handles the issue that is displayed in
```
cat A.v.timing.diff
After     | Code                                                | Before    || Change    | % Change
---------------------------------------------------------------------------------------------------
0m01.44s  | Total                                               | 0m01.56s  || -0m00.12s | -7.92%
---------------------------------------------------------------------------------------------------
0m00.609s | Chars 163 - 208 [Definition~foo1~:=~Eval~comp~i...] | 0m00.627s || -0m00.01s | -2.87%
0m00.527s | Chars 069 - 162 [Definition~foo0~:=~Eval~comp~i...] | 0m00.552s || -0m00.02s | -4.52%
0m00.304s | Chars 000 - 026 [Require~Coq.ZArith.BinInt.]        | 0m00.379s || -0m00.07s | -19.78%
   N/A    | Chars 027 - 068 [Declare~Reduction~comp~:=~nati...] | 0m00.006s || -0m00.00s | -100.00%
0m00.s    | Chars 027 - 068 [Declare~Reduction~comp~:=~vm_c...] |    N/A    || +0m00.00s | N/A
--- A.v.timing.diff.desired.processed	2018-03-23 22:22:19.000000000 +0000
+++ A.v.timing.diff.processed	2018-03-23 22:22:19.000000000 +0000
@@ -1,4 +1,4 @@
- N/A | Chars 27 - 68 [Declare~Reduction~comp~:=~nati] | ms || -ms | N/A
+ N/A | Chars 27 - 68 [Declare~Reduction~comp~:=~nati] | ms || -ms | -%
 ------
 ------
 After | Code | Before || Change | % Change
```
where, because `Declare Reduction` takes 0.006s rather than 0s, the %
change shows up as -100% rather than N/A.

0 files changed, 0 insertions, 0 deletions