Learn English – a word for doing something that you don’t want to do

You may choose one of:

• Unavoidable
• Inevitable
• Ineluctable

or probably a more relevant wrod to your case:

• Inescapable

In the sentence

The only building in sight was a small block of yellow brick sitting on the edge of the waste land, a sort of compact Main Street ministering to it, and contiguous to absolutely nothing.

I think that the author is simply saying that the block (or rectangular structure) of yellow brick is contiguous (next door) to nothing, and that the "compact Main Street" (that is, public road of modest size) leads up to it.

Under this reading, the "it" in "ministering to it" is the "block of yellow brick" (a commercial structure large enough to accommodate an empty and unrented shop, an all-night restaurant, and car repair shop); the street is "ministering" to the yellow building because it exists only to connect the building to the intercity roadway that (Fitzgerald points out earlier in the chapter) parallels a railway line on the edge of a "waste land" (which is, in fact, a tract of land covered with ashes—presumably a dump for incinerated garbage from New York City); and the building is contiguous to nothing because it is the only building on this spur street off the main roadway.

The further notion implied by "Main Street" here (as Tim Lymington notes in his answer) is that the three-business commercial building is effectively the business district of the ash dump community—except that there is no real community: no homes, no municipal buildings, no retail shops to serve a town or village of permanent residents; just a place where laborers at the dump can buy a meal and another place where passing motorists can get their cars repaired.