sfcgal test failures on PostGIS 2.4

[robe]

I had fixed this for 2.3, 2.5, 3.1 but can't find associated ticket. So doing separate ticket for 2.4

13:14:09  regress_sfcgal .. failed (diff expected obtained: /home/jenkins/tmp/pgis_reg_2cec61e64a94dab4560149b68fc9948ad91d5ed5/test_123_diff)
13:14:09 -----------------------------------------------------------------------------
13:14:09 --- regress_sfcgal_expected	2020-06-09 07:25:44.262309000 -0500
13:14:09 +++ /home/jenkins/tmp/pgis_reg_2cec61e64a94dab4560149b68fc9948ad91d5ed5/test_123_out	2020-06-09 07:31:51.543594000 -0500
13:14:09 @@ -10,6 +10,6 @@
13:14:09  ST_MinkowskiSum|MULTIPOLYGON(((0 0,1 0,5 0,5 1,4 1,0 1,0 0)))
13:14:09  ST_StraightSkeleton|MULTILINESTRING((1 1,1.5 1.5),(2 1,1.5 1.5),(2 2,1.5 1.5),(1 2,1.5 1.5))
13:14:09  intersection_geos|POINT(0 0)
13:14:09 -intersection_sfcgal|POINT(0 0)
13:14:09 +intersection_sfcgal|POINT(-0 -0)
13:14:09  ERROR:  Can't find foo geometry backend
13:14:09  ERROR:  Can't find  geometry backend
13:14:09 -----------------------------------------------------------------------------

13:14:11  sfcgal/regress_ogc .. failed (diff expected obtained: /home/jenkins/tmp/pgis_reg_2cec61e64a94dab4560149b68fc9948ad91d5ed5/test_129_diff)
13:14:11 -----------------------------------------------------------------------------
13:14:11 --- sfcgal/regress_ogc_expected	2020-06-09 07:25:44.266866000 -0500
13:14:11 +++ /home/jenkins/tmp/pgis_reg_2cec61e64a94dab4560149b68fc9948ad91d5ed5/test_129_out	2020-06-09 07:31:53.610383000 -0500
13:14:11 @@ -88,7 +88,7 @@
13:14:11  NOTICE:  Self-intersection
13:14:11  isvalid|f
13:14:11  isvalid|t
13:14:11 -intersection|POINT(0 0)
13:14:11 +intersection|POINT(-0 -0)
13:14:11  difference|MULTILINESTRING((0 -2,0 -10),(0 10,0 2))
13:14:11  boundary|MULTILINESTRING((0 0,0 10,10 10,10 0,0 0),(2 2,2 4,4 4,4 2,2 2))
13:14:11  symdifference|GEOMETRYCOLLECTION(LINESTRING(2 2,4 4),LINESTRING(10 10,20 20),POLYGON((0 0,0 10,10 10,10 0,0 0),(4 4,2 4,2 2,4 2,4 4)))
13:14:11 -----------------------------------------------------------------------------

Both debbie and travis exhibiting this

[Regina Obe <lr@…>]

In 84540ae/git:

Ensure sfcgal tests pass regardless version of sfcgal. Closes #4703

[Regina Obe <lr@…>]

In 99cd7a1/git:

Missed spot. Ensure sfcgal tests pass regardless version of sfcgal. Closes #4703