Add -Bsymbolic linker flag to hide sqlite symbols

[link2xt]

This prevents electron, which links against SQLite,
from overriding SQLCipher used in libdeltachat during dynamic linking.

Fixes #538

[Simon-Laux]

the export works now, I got an electron error which is probably unrealated, but I'll still post it here for reference:

[48279:0302/214110.712573:ERROR:vaapi_wrapper.cc(1123)] vaQuerySurfaceAttributes failed, VA error: invalid parameter
[48279:0302/214110.712733:ERROR:vaapi_wrapper.cc(1070)] FillProfileInfo_Locked failed for va_profile VAProfileH264Main and entrypoint VAEntrypointVLD
[48279:0302/214110.712776:ERROR:vaapi_wrapper.cc(1123)] vaQuerySurfaceAttributes failed, VA error: invalid parameter
[48279:0302/214110.712811:ERROR:vaapi_wrapper.cc(1070)] FillProfileInfo_Locked failed for va_profile VAProfileH264High and entrypoint VAEntrypointVLD

to be clear export worked on linux with this pr in both node and electron

[dotlambda]

Signal added another flag, I don't know if that's something we also want: signalapp/better-sqlite3#3

[dotlambda]

There is a related issue in the Matrix ecosystem: matrix-org/seshat#102