zlib: remove LDFLAGS workaround.

[ericonr]

Added in 4d39b70 without explanation as
to why.

We also revbump to rebuild the binary. On x86_64-musl, old libz.so,
built with gcc 7, is using a 2132KB RE mmap when dynamically linked,
probably because of a 0x200000 alignment required for the RE section.
After rebuilding, 96KB are used, with the actual RE mmap reduced to 56K.
The new alignment is 0x1000.

General

• This is a new package and it conforms to the quality requirements

Have the results of the proposed changes been tested?

• I use the packages affected by the proposed changes on a regular basis and confirm this PR works for me
• I generally don't use the affected packages but briefly tested this PR