How to interpret commands between colon and first tab ?

[Ewan Delanoy]

     Hello all, I'm rather new to make (only used it without reading the
   manual so far).
     The "all" target in a makefile for gcc5-2.0 looks like below. Notice
   that this code snippet contains
   no tab at all after the colon (the first tab is much further in the
   code). I could not find in the
   GNU make manual a mention of how make treats those particular regions
   in the makefile.
      I thought about secondary expansion but this makefile nowhere uses
   .SECONDARYEXPANSION
     AFAIK, this will be interpeted as "make syntax" as opposed to "shell
   syntax" used in recipes. Where
   does the manual explain how, for example, the commands between `` are
   read ?

     Any help appreciated.

   Ewan

   all:
   #### host and target specific makefile fragments come in here.
   # The -mdynamic-no-pic ensures that the compiler executable is built
   without
   # position-independent-code -- the usual default on Darwin. This fix
   speeds
   # compiles by 3-5%.  Don't add it if the compiler doesn't also support
   # -mno-dynamic-no-pic to undo it.
   DARWIN_MDYNAMIC_NO_PIC := \
   `case ${host} in i?86-*-darwin* | powerpc-*-darwin*) \
      $(CC) -S -xc /dev/null -o /dev/null -mno-dynamic-no-pic 2>/dev/null
   \
      && echo -mdynamic-no-pic ;; esac`
   DARWIN_GCC_MDYNAMIC_NO_PIC := \
   `case ${host} in i?86-*-darwin* | powerpc-*-darwin*) \
      $(CC) -S -xc /dev/null -o /dev/null -mno-dynamic-no-pic 2>/dev/null
   \
      || echo -mdynamic-no-pic ;; esac`