Only accept xelatex for building PDF docs

[steveklabnik]

None of the others work, so let's remove them.

Fixes #17220.

r? @brson

[alexcrichton]

Looks like there's a tidy error (makefiles won't parse).

Otherwise r=me

[steveklabnik]

$ git diff
diff --git a/mk/docs.mk b/mk/docs.mk
index 547ad96..71b2533 100644
--- a/mk/docs.mk
+++ b/mk/docs.mk
@@ -87,7 +87,7 @@ endif

 # Check for xelatex

-ifeq($(CFG_XELATEX),)
+ifeq ($(CFG_XELATEX),)
     CFG_LATEX := $(CFG_XELATEX)
     XELATEX = 1
   else

dammit, make

[steveklabnik]

@bors: r=alexcrichton 7d4f068

[steveklabnik]

This seems to have not be seen by @bors :( @alexcrichton ideas?

[sfackler]

@bors: r=alexcrichton 7d4f068

maybe?

[sfackler]

Looks like that did it 😕

[bors]

⌛ Testing commit 7d4f068 with merge 00df325...

[steveklabnik]

@sfackler: ❤️ yeah, no idea there

[bors]

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-x-android-t, auto-mac-32-opt, auto-mac-64-nopt-t, auto-mac-64-opt, auto-win-32-nopt-t, auto-win-32-opt, auto-win-64-nopt-t, auto-win-64-opt