Build fails with sfcgal master

[Algunenano]

Lately sfcgal applied 2 changes that modify the build:

• Changed where libtoolize places the .la files (​https://github.com/Oslandia/SFCGAL/pull/207). This breaks our Travis latest build.

• Add pkg-config descriptor file (​https://github.com/Oslandia/SFCGAL/pull/205).

This is the error we get with the current master (​https://travis-ci.org/github/postgis/postgis/jobs/669581694):

/bin/bash ../../libtool --mode=link gcc -std=gnu99 -g -O2 -mtune=generic -fno-omit-frame-pointer -Werror -Wall -Wextra -Wformat -Werror=format-security -Wno-unused-parameter -Wno-implicit-fallthrough -Wno-unknown-warning-option -Wno-cast-function-type -fno-math-errno -fno-signed-zeros  -fPIC -DPIC -I../rt_core -I../../liblwgeom  -I/usr/local/include -I/usr/local/include   ../rt_core/librtcore.a raster2pgsql.o -Wl,-Bsymbolic-functions -Wl,-z,relro -lm -static ../../liblwgeom/liblwgeom.la -L/usr/local/lib -lgdal  -L/usr/local/lib -lgeos_c  -lc -o raster2pgsql
libtool: warning: library '/usr/local/lib/libSFCGAL.la' was moved.
*** Warning: Linking the executable raster2pgsql against the loadable module
*** libSFCGAL.so is not portable!
libtool:   error: cannot find the library 'lib/libSFCGAL.la' or unhandled argument 'lib/libSFCGAL.la'
make[2]: *** [Makefile:84: raster2pgsql] Error 1
make[2]: Leaving directory '/src/postgis/raster/loader'
make[1]: *** [Makefile:35: rtloader] Error 2
make[1]: *** Waiting for unfinished jobs....

I don't know if supporting pkg-config (instead of defaulting to sfcgal-config) will fix this or this is a bug in either or build or sfcgal's new configuration.

[Algunenano]

Reported at ​https://github.com/Oslandia/SFCGAL/issues/215

Fix proposed at ​https://github.com/Oslandia/SFCGAL/pull/216

[Algunenano]

Fixed upstream by removing the libtool support.

Latest now compiles and runs CI: ​https://travis-ci.org/github/postgis/postgis/jobs/678678444

Raster is broken (again) probably due to GDAL changes (seems like rounding).